Revert^4 "Set block device as RO/RW before mount"

This reverts commit 1df3536b.

Previous land got reverted because of selinux denial, which is
already taken care of in aosp/3314877

Reason for revert: b/349507086

Change-Id: Id642b4d8726c72f324e369d8506c78eacea331e3