Add test for MediaScanner misbehavior

Back in Eclair, a bug that could cause files to be deleted from the
sd card was fixed. Unfortunately, some OEM customizations caused this
bug to reappear in subsequent OEM releases.
Add a check for the misbehavior to ensure it won't happen again.

Change-Id: I80655d0a8493e53aa7cd8f4c8e5e6181fcbd9c9e

cherrypicked from ICS