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.
@bzwei maybe this can be refactored in follow up PRs into objects to avoid the same check `if state =='scanning'` in multiple methods.