Merge "fs_mgr: Use /proc/mounts to check if /cache is mounted" into main am: 7881073ec8 am: ed0de0be90 am: 89dccffdbd

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

Change-Id: I1469db2a38592da04806e4d322d9d0f6be596211
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>