Make sdb.delete() actually call a delete in Redis

Looks like this was missed when copy-pasting the sdb.get() method.

salt/sdb/redis_sdb.py

@@ -81,4 +81,4 @@ def delete(key, profile=None):
     redis_kwargs = profile.copy()
     redis_kwargs.pop('driver')
     redis_conn = redis.StrictRedis(**redis_kwargs)
-    return redis_conn.get(key)
+    return redis_conn.delete(key)