[FIXED JENKINS-13448] Added additional checks if Guice will be able to create injector to exclude missing extension poins.

displayed run's estimated duration in api

The javadoc of MavenReporter states clearly that preBuild/postBuild is
only once per the entire build, but the previous code was calling it at
the same timing as enter/leaveModule.

This is now fixed.

Also removed a duplicate constant