Ensure user storage is prepared after mount

After adoptable storage mount returns, PackageManager still needs to
prepare user storage (mkdirs like data/, app/, user/...). Attempting
to use the new storage before these directories are ready will likely
fail.

Test: atest AdoptableHostTest
Bug: 135341433
Change-Id: Ie3488eed7c4b1b8c6e663ffed8a3fa2f7d909b04
1 file changed