fs_mgr: remount reboot if overlayfs got setup

Cosmetic fix.

If overlayfs gets setup by the remount command, ask user to reboot
since the device is not 100% in a state to run, and is merely only
in a state to take push and sync operations.

overlayfs is only truly ready for developing and running if the
overly mounts had occurred in first stage init, this happens when
the device is rebooted.

We did not completely remove overlapping dead ext4 dedupe code in a
previous change, complete the process.

Simplification for adb remount, the message:

    Now reboot your device for settings to take effect

will only occur on the pass that causes the overlays to be populated,
in the same boot session. If subsequent, and ineffectual in any case,
remount command occurs again, it will not request a reboot.

Test: adb-remount-test.sh
Bug: 130131892
Change-Id: I7c4f408546687c49249883e2641b9bc63f68afd0