SafetyWarningDialog crash

The cause of the problem is that cancel() and cleanUp() are called
in the ACTION_CLOSE_SYSTEM_DIALOGS broadcast processing, and cancel()
triggers the onDismiss callback, which in turn triggers cleanUp() again,
resulting in cleanUp() being called twice.
From a design perspective, cleanUp() should only be called once.

bug: 433128308
(cherry picked from https://android-review.googlesource.com/q/commit:4d8025715adae7bc23e6346f20a6962148b7442d)
Flag: EXEMPT bugfix
Merged-In: Ifa8d2d20d2f73abd357ca3483bd5f427da754cab
Change-Id: Ifa8d2d20d2f73abd357ca3483bd5f427da754cab