Clean up the uncrypted OTA package on bootup.

An OTA package needs to be uncrypted before rebooting into recovery if
it sits on an encrypted /data partition. Once uncrypt gets started, we
cannot re-run it on the package again. Because the file may have been
fully or particially uncrypted and we may end up with a corrupt file
under recovery. Always clean up the package when the device boots into
the normal system to avoid that.

Bug: 24973532
Change-Id: I91682c103d1f2b603626c4bf8d818bced71e3674