HWComposer: Relax port ID duplicate check

Recently, a fatal check guard was added in allocateVirtualDisplay()
against duplicate port IDs. This check seem to have uncovered an
pre-existing issue that causes a system crash on Comet while using an
external display.

We relax the fatal check guard while we investigate the issue to avoid
a full native crash.

Flag: EXEMPT bugfix
Bug: 412011951
Bug: 413414541
Test: HotplugTest#rejectsHotplugOnActivePortsDuplicate
Change-Id: I17a71b07b4f3e7f1c606fa9098b3497611263f0d