core:unlock_entity is not locating locked snapshot

fix caused a regression when handling disk , sql statement is prepared
but not executed

Change-Id: I4a991183517c580d651f6a0e7c92749b66a163b3
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=958370
Signed-off-by: Eli Mesika <emesika@redhat.com>