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.
Create nested modules separately.  Note that (oddly) `module BlackBoxMgr::StateMachine` is different from `module BlackBoxMgr; module StateMachine` with respect to constant lookup and scoping.