If anything bad happens and unlocking fails

If anything bad happens and unlocking fails
(here clvmd crashed in the middle of operation),
lock is not removed from cache - here is one example:

locking/cluster_locking.c:497       Locking VG V_vg_test UN (VG) (0x6)
locking/cluster_locking.c:113   Error writing data to clvmd: Broken pipe
locking/locking.c:399         <backtrace>
locking/locking.c:461         <backtrace>
  Internal error: Volume Group vg_test was not unlocked

Code should always remove lock info from lvmcache and update counters
on unlock, even if unlock fails.