- make snapper capable handling inactive lvm snapshots

Hi, 
this is it. Instead of checking LVM2 version I added retry command without -K option. Checking lvm2 version would involve fork/exec anyway so I think its less work to do it this way.

I also added deactivation after umount() Filesystem method. But this is will cause implicity deactivation also on older lvm2 version. Some users may be confused by this new behaviour (by this confusion would apply to lvm2 change as well, I think).

Small change to checkSnapshot() where I need to detect inactive snapshots as well.

Passed testsuite-real and also few cmd line tests (diff, status, xadiff, mount, umount)