Avoid system reboot while invalidate LegacyGlobalAction

normally custom global action is running at android.ui thread, but
it is running at main thread if default global action showing
without a status bar. these two threads will lead to
CalledFromWrongThreadException

Fix:
Always run at android.ui thread

CRs-Fixed: 2588661
Test: Monkey test
Change-Id: Ie02b98daf3ef0930f531e68bedbfbcf4bd6794bc