qa: adjust for old snapshot counts during comparison

qa: adjust for old snapshot counts during comparison

This is pacific only commit since in master, the snap-schedule module
uses vfs-ceph backed libcephsqlite which seems to preserve the
snapshots stats (created_count, etc..) on ceph-mgr restarts. Pacific
uses in-memory db (serialized to a RADOS object) which seems to
reset these stats when ceph-mgr is restarted.

Also, remove `db_count' assert check as it doesn't make sense.

Signed-off-by: Venky Shankar <vshankar@redhat.com>