[EventHubs] ignore the generated certs/ folder (Azure#20287)

* [EventHubs] ignore the generated certs/ folder

It is re-generated in every build and used for mock-hub testing

* Revert "[EventHubs] ignore the generated certs/ folder"

This reverts commit 7fed060.

* [engsys] ignore *.srl files

They are files created and used by OpenSSL.

Author: jeremymeng

.gitignore

@@ -120,6 +120,7 @@ Thumbs.db
 *.pfx
 *.pem
 *.key
+*.srl
 
 # WebStorm #
 .idea/