[JENKINS-38903] Split Exception handling for node provision and adding to Jenkins (#2591)

* [JENKINS-38903] Split Exception handling for node provision and adding to Jenkins

* Defined new static helper methods that ensure exceptions are not propagated

* Added onCommit and onRollback signals to CloudProvisioningListener

Added the new signals to be able to notify the state after Jenkins.addNode(Node)
All Listener's calls moved to an exception-tolerant static helpers

* Added @Nonnull annotation
Changed the method signature CloudProvisioningListener.onRollback()

* Re-throw Error in the fireOnXXX()
Removed re-thrown Throwable in the main try/catch block
	(an instance of the Error is handled separately)

* Handling of Error changed

* Fixed Error instance handling in NodeProvisioner.fireOnFailure()