Merge "fs_mgr: move mkdir(mount_point) to prepare_fs_for_mount()" am: a1411e4311 am: 9ed5699204 am: d041e1d38d

Original change: https://android-review.googlesource.com/c/platform/system/core/+/1505939

Change-Id: Ie2344e1b96f4de76071482f19c58f403845eccc3