libsnapshot: Quell error spam during factory data resets.

QuerySnapshotStatus assumes IsSnapshotDevice() would return true.

Additionally, recovery does not have access to /dev/loop-control, which
cannot be used by libfiemap anyway. Access it on-demand instead of
preemptively.

Bug: N/A
Test: manual test
Change-Id: I0f746870d7a8ec6d666f0bdd2fef3464b214928b