Fix memory lock imbalance in locking code.

Fix memory lock imbalance in locking code.

(This affects only cluster locking because only cluster
locking module set LCK_PRE_MEMLOCK.)

With currect code you get
# vgchange -a n
  Internal error: _memlock_count has dropped below 0.
when using cluster locking.

It is caused by _unlock_memory calls here

  if ((flags & (LCK_SCOPE_MASK | LCK_TYPE_MASK)) == LCK_LV_RESUME)
     memlock_dec();

Unfortunately it is also (wrongly) called in immediate unlock
(when LCK_HOLD is not set) from lock_vol
(LCK_UNLOCK is misinterpreted as LCK_LV_RESUME).

Avoid this by comparing original flags and provide memlock
code type of operation (suspend/resume).