Fix udev synchronization for no-locking mode

Fix udev synchronization for no-locking mode

Instead of implicitly syncing udev operation in clustered and
file locking code -  call synchronization directly in lock_vol() when
the operation unlocks VG

The problem is missing implicit fs_unlock() in the no_locking code.
This is used with --sysinit on read-only filesystem locking dir.
In this case vgchange -ay could exit before all udev nodes are properly
synchronised and may cause problems with accessing such node right after
vgchange --sysinint command is finished.

Add test case for vgchange --sysinit.