Bug 975794: Move oo-admin-cartridge operations to %posttrans

The oo-admin-cartridge command isn't safe to use in %post the way we currently
install the package; during %post, the previous RPM version files haven't been
cleaned up, meaning we install from a source tree containing a mixture of old
and new cartridge version files.

Move the operation to %posttrans, which guarantees the install picks up the final
installed package state, and thus only files from the new RPM installation.