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

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

Change-Id: I6c17bc5c5214c5a2e9573e96999f9edd4357798c