Set AppErrorDialog result during dismissal if it isn't already set

The system watch dog was triggering because all binder threads were
waiting for AppErrorResult#set() to be called which never happened.
One situation where this can occur is if a process continues to crash
and the activity manager marks the process as bad there by causing it
to kill the process immediately which causes a binder death
notification that automatically dismisses the app error dialog before
the user ACKs it.
We now set the result during dialog dismissal if it isn't already set.

Bug: 22141958
Change-Id: If3ac116df5e29c6fba43ee556a859ad3c84c66f3