Fix memory lock imbalance in lv_suspend if already suspended.

Fix memory lock imbalance in lv_suspend if already suspended.

pvmove suspends all moved LVs + pvmoveX mirrored LV itself.

This suspends even underlying pvmoveX and following explicit
suspend call is just noop.

But in resume the pvmoveX volume is no longer underlying
device for moved LVs, so it performs full resume with memlock
decrease.

Code must call memlock_inc() if suspend is requested, volume
is already suspended and error is not requested.