Merge "fs_mgr: Use /proc/mounts to check if /cache is mounted" into main am:...

Merge "fs_mgr: Use /proc/mounts to check if /cache is mounted" into main am: 7881073e am: ed0de0be am: 89dccffd am: 35511b65

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2745619



Change-Id: I9789822830aa66248c7bc26dd2543579f04b78a9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>