I came to this thread because I was trying to figure out why a retakes server wouldn't go to the max rounds after setting the first 2 commands listed above. I found that my issue was that the mp_timelimit was a low value so it was only playing for 5 minutes then ending the match.
Code:
mp_maxrounds 35 // Set the number of rounds you would like to play
mp_match_can_clinch 0 // Ensure we always play the number of rounds set in mp_maxrounds
mp_timelimit 9999 // Let the match go until the round conditions are met