Disabling postinstall, preuninstall and postuninstall scripts on RPM based hosts


This kind of fixes https://github.com/flapjack/omnibus-flapjack/issues/13 

I asked on #chef if there was a way to have different files based on the distro, there doesn't seem to be one.
Alternative approaches are to put a lot of if statements in this scripts.



But imvho all of the actions in here do belong in cfgmgmt.
This probably needs further discussion.