Unmount public volume if FUSE mount fails am: f71707916f am: 0f9690e391 am: 96832d4ef8 am: 526499eb97

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/vold/+/11900947

Change-Id: Ia663cc61ff7af0332676f298d2e9166c3aeabbe5