onAccountsUpdated shouldn't be called back after listener unregistered

There is a problem of AccountManager that onAccountsUpdated() is
called back even after the OnAccountsUpdatedListener is unregistered.
It may cause application crash.

For example, when rotating a tablet 180 degree with Settings apk
running, com.android.settings.Settings is re-launched 2 times
successively. (Destroy->Create->Destroy->Create)
It repeats adding&removing OnAccountUpdatedListener.

When dialog was being opened in the following cases,
NullPointerException at BackStackRecord.getBreadCrumbTitle()
was happened on 10 inch tablet which has 2 panes on Settings.
* Settings > Language&input > Language
* Settings > Language & input > Text-to-speech output > Speech rate
* Settings > Wi-Fi > Menu > Advanced > Keep Wi-Fi on during sleep
* Settings > Wi-Fi > Menu > Wi-Fi Direct > Rename device

This fix prevents the undesirable callback.

Change-Id: I081f69c90539cca821cf686b4587495135f375e4