libsnapshot: NeedSnapshotsInFirstStageMount don't test for IsRecovery

Init skips first stage mount entirely in recovery, so
the check is useless. Also, __ANDROID_RECOVERY__ is always
set for first stage init.

Also add logs if rollback indicator is set.

Fixes: 149956852
Test: apply OTA, manually rollback, reboot, see rollback indicator
Change-Id: Iac967baf4b51ea5ce9f6eb962a33cb7ee5819c1d
Merged-In: Iac967baf4b51ea5ce9f6eb962a33cb7ee5819c1d