Update .travis.yml

potential fix for passing builds being labeled as Travis failures.

Author: DellaBitta

.travis.yml

@@ -114,3 +114,6 @@ script:
                 make -C examples/iot_core_mqtt_client IOTC_CLIENT_LIB_PATH=../../bin/linux IOTC_BSP_TLS=$IOTC_BSP_TLS;
         fi;
     fi;"
+  # Fix for successful builds being reported as failed in Travis.
+  # See https://github.com/travis-ci/travis-ci/issues/8082 .
+  - "ssh-agent -k"