Your examples aren't vendor code - you might have stated the true problem in the original post.
Your two options -
Have the vendor fix their code (Good luck)
or
try setting up an alias for ssh to be equal to ssh -q which may take care of the situation.
The warning isn't a bad thing - but the fact that the vendor didn't realize it could happen and code for the possiblities seems to show how well their software may be. Or, there may be a difference in the versions of ssh you are using which is causing your error (and has nothing to do with the vendor's code). And I've found in the past that vendor code can be changed (if it's a script) to get around these types of errors. If it is a script, is it downloaded to your UNIX server already or on cd?
I didn't find anything with a search that supplies an answer to changing your ssh configuration to get rid of the warning. You might want to post the exact scenerio - what type of servers involved, OS/version, ....