Allow to query all volumes

Some apps which manage their own database like Google Photos query
MediaProvider in order to synchronize between MediaProvider database and
their own database. Unfortunately, they can misunderstand that rows of
unmounted volume are deleted even though the rows are not deleted. It's
because they can be notified later than when MediaProvider is notified.

Bug: 171025568
Test: manual
Change-Id: Ic64f87bb27e54077ee736d5f67731b24d6c999f1
Merged-In: Ic64f87bb27e54077ee736d5f67731b24d6c999f1
1 file changed