Isolate flow system tests, installating a flow per test

The test "Appending messages to a file" is flaky,
but not only because the flow is exercised too soon
(i.e. publishing events just after moving the flow definition under the
tedge flow directory). But also, because of the following bugs:

- The timer of periodic sources are not properly registered.
  This error was masked by other flows registering step timers.
- The inotify messages are not always leading to a proper reload.
  The root cause being that depending of the command used to deploy a
  flow, inotify might wrongly notify that a flow has been modified and
  not added.

Signed-off-by: Didier Wenzek <didier.wenzek@free.fr>

Author: didier-wenzek

tests/RobotFramework/tests/tedge_flows/flows/append-to-file.toml renamed to tests/RobotFramework/tests/tedge_flows/flows/input-ext/append-to-file.toml

@@ -97,7 +97,6 @@ Running tedge-flows
     Execute Command    tedge mqtt sub test/count/e --duration 2s | grep '{}'
 
 Consuming messages from a process stdout
-    # Assuming the flow journalctl-follow.toml has been properly installed
     Install Journalctl Flow    journalctl-follow.toml
     ${test_start}    Get Unix Timestamp
     Restart Service    tedge-agent
@@ -106,7 +105,6 @@ Consuming messages from a process stdout
     [Teardown]    Uninstall Journalctl Flow    journalctl-follow.toml
 
 Consuming messages from a process stdout, periodically
-    # Assuming the flow journalctl-cursor.toml has been properly installed
     Install Journalctl Flow    journalctl-cursor.toml
     ${test_start}    Get Unix Timestamp
     Restart Service    tedge-agent
@@ -115,32 +113,35 @@ Consuming messages from a process stdout, periodically
     [Teardown]    Uninstall Journalctl Flow    journalctl-cursor.toml
 
 Consuming messages from the tail of file
-    # Assuming the flow tail-named-pipe.toml has been properly installed
+    Install Flow    tail-named-pipe.toml
     ${start}    Get Unix Timestamp
     Execute Command    echo hello>/tmp/events
     Should Have MQTT Messages    topic=log/events    message_contains=hello    minimum=1    date_from=${start}
+    [Teardown]    Uninstall Flow    tail-named-pipe.toml
 
 Consuming messages from a file, periodically
-    # Assuming the flow read-file-periodically.toml has been properly installed
+    Install Flow    read-file-periodically.toml
     Execute Command    echo hello >/tmp/file.input
     Execute Command    tedge mqtt sub test/file/input --duration 1s | grep hello
     Execute Command    echo world >/tmp/file.input
     Execute Command    tedge mqtt sub test/file/input --duration 1s | grep world
     Execute Command    rm /tmp/file.input
     Execute Command
-    ...    tedge mqtt sub test/file/input --duration 1s | grep 'Error in /etc/tedge/flows/read-file-periodically.toml'
+    ...    tedge mqtt sub test/file/input --duration 1s | grep 'Fail to poll /tmp/file.input'
     Execute Command    echo 'hello world' >/tmp/file.input
     Execute Command    tedge mqtt sub test/file/input --duration 1s | grep 'hello world'
+    [Teardown]    Uninstall Flow    read-file-periodically.toml
 
 Appending messages to a file
-    # Assuming the flow append-to-file.toml has been properly installed
+    Install Flow    append-to-file.toml
     Execute Command    for i in $(seq 3); do tedge mqtt pub seq/events "$i"; done
     Execute Command    grep '\\[seq/events\\] 1' /tmp/events.log
     Execute Command    grep '\\[seq/events\\] 2' /tmp/events.log
     Execute Command    grep '\\[seq/events\\] 3' /tmp/events.log
+    [Teardown]    Uninstall Flow    append-to-file.toml
 
 Publishing transformation errors
-    # Assuming the flow publish-js-errors.toml has been properly installed
+    Install Flow    publish-js-errors.toml
     ${start}    Get Unix Timestamp
     Execute Command    tedge mqtt pub collectd/foo 12345:6789
     Should Have MQTT Messages
@@ -167,6 +168,7 @@ Publishing transformation errors
     ${message}    JSONLibrary.Convert String To Json    ${messages[0]}
     Should Be Equal As Integers    ${message["time"]}    12345
     Should Be Equal As Integers    ${message["b"]["c"]}    6789
+    [Teardown]    Uninstall Flow    publish-js-errors.toml
 
 
 *** Keywords ***
@@ -188,6 +190,14 @@ Uninstall Journalctl Flow
     [Arguments]    ${definition_file}
     Execute Command    cmd=rm -f /etc/tedge/flows/${definition_file}
 
+Install Flow
+    [Arguments]    ${definition_file}
+    ThinEdgeIO.Transfer To Device    ${CURDIR}/input-ext/${definition_file}    /etc/tedge/flows/
+
+Uninstall Flow
+    [Arguments]    ${definition_file}
+    Execute Command    cmd=rm -f /etc/tedge/flows/${definition_file}
+
 Configure flows
     # Required by tail-named-pipe.toml
     Execute Command    mkfifo /tmp/events