Fix PrivateVolumeSettings be launched repeatedly

Symptom:
After manually pull out the removable sd card or usb storage in
StorageSettings screen, it automatically moves to
PrivateVolumeSettings screen. This time, launching
PrivateVolumeSettings Activity is triggered six times and end-user
has to press back key six times to exit PrivateVolumeSettings
screen.

Root cause:
When sd card is pulled out, StorageSettings got three state change
event (UNMOUNTED, BAD_REMOVAL and onDiskDestroyed) through
StorageEventListener that triggers launching PrivateVolumeSettings
screen. In addition StorageSettings register the listener two
times, then StorageSettings receives six event in total.
Therefore, PrivateVolumeSettings screen is launched six times.

Solution:
Skip launching PrivateVolumeSettings if it's already triggered.
And removed the duplicated listener registration.

Bug: 67612903

Change-Id: Iabef51677a393977b7be29fc54aa050434213500