Disable bmgr if BMS is not running

If BMS is not running, we should not run any bmgr commands and print an
error. This can occur after a device with a lockscreen reboots and has
not unlocked yet, as the backup service is not active before unlocking.

Bug: 80691476
Test: 1) Device with lock + adb reboot -> run any 'adb shell bmgr'
command -> prints error
2) Device with no lock + adb reboot -> run any 'adb shell bmgr' command
-> success

Change-Id: I101b61d18a637cdb945ffc4a5e989a5dd270ee32