[automerger skipped] Merge "fastbootd: Unmount /cache before flashing." into rvc-dev am: ab4a2621aa -s ours

am skip reason: Change-Id I8a86bc4d12e4b3be020bbe47e02262a5aaa913a7 with SHA-1 2ffc31b090 is in history

Change-Id: Id6ae907072764761a5b51deb4aff81f7e4debb8a