DERBY-6453 Remove dead code in InsertResultSet and flag skipCheckConstraints

Patch _*cleanup-misc-3*_ which removes dead code but inserts asserts
in sane mode if we should somehow end up with triggers in bulk insert
mode and also removes a boolean variable in some interfaces which was
always called with false: {{skipCheckConstraints}}.
It adds a new test case, {{CheckConstraintTest#testbulkInsert}}.



git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1556938 13f79535-47bb-0310-9956-ffa450edef68