rules: import previous SYSTEMD_READY state for suspended DM devices and skip other...

rules: import previous SYSTEMD_READY state for suspended DM devices and skip other rules

We can't get any FS meta-data from a suspended device. Hence defer
making any plugged/unplugged decisions, i.e. we just import whatever was
previous state and skip processing all other rules.

Thanks Lennart Poettering <lennart@poettering.net> for suggesting this
solution.