Fixed the IllegalStateException on removing account

We display a dialog in AccountManager.removeAccountAsUser() callback, but at that
time fragment is onstop() which causes the IllegalStateException.

Fixes: 133253227
Fixes: 135004255
Test: make RunSettingsRoboTests -j56 ROBOTEST_FILTER=com.android.settings.accounts
      make RunSettingsRoboTests -j56 ROBOTEST_FILTER=com.android.settings.core
      make RunSettingsRoboTests -j56 ROBOTEST_FILTER=com.android.settings.dashboard

Change-Id: I8534e8f7118234f6346607415698f9f91c3e5ffb
(cherry picked from commit d843ee85)