DERBY-6628 Intermittent error in TriggerGeneralTest

Patch derby-6628b filters away any locks on system tables stemming
from (re)compilations of statements, since compilation locks is not of
primary interest in this test.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1621215 13f79535-47bb-0310-9956-ffa450edef68