Fix IDEUI-221 Better app health check

Fix some bugs:
* disable app health check if application is not an HTTP reachable one,
* fix message,
* if project is stopped, canceled or failed, we now stop checking for
application health,
* correct stopCheckingAppHealth bugs.
Merge pull request #269 from stephanedaviet/IDEUI-221

Fix IDEUI-221 Better app health check