fs_mgr_remount: fix a typo

Replacing "ro.boot.vbmeta.devices_state" with
"ro.boot.vbmeta.device_state" to check if the device is locked.

Bug: 132224452
Test: tree hugger
Change-Id: If4f312730cc82ad5a5d5104a7aca8b9691cf6600
(cherry picked from commit 2badf73b)