Replace the external state_machine with an internal implementation

https://bugzilla.redhat.com/show_bug.cgi?id=1089061

This work refactored Job and its subclasses to use an internal implementation of state machine, removed the dependency of the state_machine gem.
Can we make it so the statemachine just does a no-op if the method doesn't exist?...then we don't need the stub nor the comment.