Merge "Revert "first_stage_mount: Bind mount /system after switch root"" am:...

Merge "Revert "first_stage_mount: Bind mount /system after switch root"" am: e321b113 am: a367bdbc

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2159462



Change-Id: Ib74e85abc09cc40430171e02b3a370c303b953cb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>