s3-param: Make "rlimit_max below minimum Windows limit" notification less scary

s3-param: Make "rlimit_max below minimum Windows limit" notification less scary

The fix to bug #6837 results in messages from testparm that look
like a misconfiguration even though they aren't:

 rlimit_max: rlimit_max (8192) below minimum Windows limit (16384)

Apply a slight change in wording ("increasing rlimit_max to minimum
Windows limit") to make it clearer that the user has done nothing
wrong.  (Similarly for sysctl_max.)

Reported-by: Miguel Medalha <miguelmedalha@sapo.pt>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>