[mlag] fix log print sequence (sonic-net#1730)

#### What I did
fix error log variable print sequence, otherwise it is confusable 
#### How I did it
change the varible print sequence

#### New command output (if the output of a command-line utility has changed)
before keepalive-interval setting:
```
root@sonic:/home/admin# config mclag 1 keepalive-interval 30
MCLAG Keepalive:15 Session_timeout:30 values not satisfying session_timeout >= (3 * KA)
```
after fixing:
```
root@sonic:/home/admin# config mclag 1 keepalive-interval 30
MCLAG Keepalive:30 Session_timeout:15 values not satisfying session_timeout >= (3 * KA)
```

config/mclag.py

@@ -22,7 +22,7 @@ def mclag_ka_session_dep_check(ka, session_tmout):
     """Check if the MCLAG Keepalive timer and session timeout values are multiples of each other and keepalive is < session timeout value 
     """
     if not session_tmout >= ( 3 * ka):
-        return False, "MCLAG Keepalive:{} Session_timeout:{} values not satisfying session_timeout >= (3 * KA) ".format(session_tmout, ka)
+        return False, "MCLAG Keepalive:{} Session_timeout:{} values not satisfying session_timeout >= (3 * KA) ".format(ka, session_tmout)
 
     if session_tmout % ka:
         return False, "MCLAG keepalive:{} Session_timeout:{} Values not satisfying session_timeout should be a multiple of KA".format(ka, session_tmout)