Call verify in create-multiple

Idmap Scan previously called Verify before calling Create. OverlayConfig
should do the same. Removing the verify call caused b/149784008.

Since sSystem is marked @UnsupportedAppUsage,
createSystemAssetsInZygoteLocked could potentially be invoked in the
system server. Rather than attempting to create the overlays a second
time, first check whether the idmap must be invalidated.

Bug: 149784008
Test: running forrest using web UI
Change-Id: I5d995a87e8552bd156fb5415b2c46a08f4c1d6c5