RFR(T): 8214541: ZGC: Refactoring from JDK-8214172 may leave PhaseIterGVN::_delay_transform set

[Roland Westrelin]

http://cr.openjdk.java.net/~roland/8214541/webrev.00/

If there's no barrier to expand, the PhaseMacroExpand is executed and
sets _delay_transform but nothing resets it. Also the PhaseMacroExpand
construct sets _delay_transform so there's no need to set it explicitly
in the barrier code.

This looks trivial to me and I will push it with a single review unless
someone objects.

Roland.