pmdadm: Add function to check about dm-device to Install script
pmdadm: Add function to check about dm-device to Install script

When install pmdadm, check whether it can use dmstats metrics.
If there are no dm-devices or no dm-devices' regions,
the install script display some instruction.

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp