DERBY-6342: failure in ConglomerateSharingTest.testConstraintDrops

Accept different errors from statements that violate multiple
constraints, since it's not deterministic which constraint is checked
first.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1610373 13f79535-47bb-0310-9956-ffa450edef68