bug fix: handle multiple port settings change events signalled at once

Components can send various kinds of port settings changed events all
at once. During a full port reconfiguration this is causing problems
due to limited flexibility in the message handling design. For now,
before committing to a full port reconfiguration defer any events
waiting in the queue to be addressed to a later point.

Test: make vts -j99 BUILD_GOOGLE_VTS=true TARGET_PRODUCT=aosp_arm64 \
&& vts-tradefed run commandAndExit vts \
--skip-all-system-status-check --primary-abi-only \
--skip-preconditions --module VtsHalMediaOmxV1_0Test -l INFO

Bug: 64468705

Change-Id: I537cdd3e7d92cdc6d54168f091d7897afe541599