Wait for MediaProvider idle before checking quota.

This operation is async, and can take a bit of time. We don't require
quota to be milli-second accurate, so instead have the test only check
after MediaStore is idle.

Bug: 150027250
Test: atest StorageHostTest
Change-Id: I12ecb0bb241c7195a881d06c7fd3e3eb66148a7a
1 file changed