[MultiDB]: update sonic-db-cli output to redis-cli output format (son…

…ic-net#59)

* [MultiDB]: update sonic-db-cli output to redis-cli output format
* add codes comments and handle review request

src/swsssdk/scripts/sonic-db-cli

@@ -24,4 +24,15 @@ else:
     else:
         client = dbconn.get_redis_client(dbname)
         args = sys.argv[2:]
-        print client.execute_command(*args)
+        resp = client.execute_command(*args)
+        """
+        sonic-db-cli output format mimic the non-tty mode output format from redis-cli
+        based on our usage in SONiC, None and list type output from python API needs to be modified
+        with these changes, it is enough for us to mimic redis-cli in SONiC so far since no application uses tty mode redis-cli output
+        """
+        if resp is None:
+            print ""
+        elif isinstance(resp, list):
+            print " ".join(resp)
+        else:
+            print resp