There is a way to surrender but it requires all 5 of you to do it, if one person doesn't follow through then it won't work so for this reason you should only do the following if you're grouped:
everyone make sure that they have the console available (-console in the launch options, make sure it's bound to something you can use).
When you want to ditch the game as 5 everyone opens the console and uses the command disconnect.
If all 5 of you stay disconnected for 10s (might be upto 30, don't remember that well) the game will end with the disconnecting team taking the loss. No one will be given an abandon cruicially. If however, one person stays then it will do the usual 5 minute timeout and the first person to have dropped will be given an abandon.
Once you have disconnected wait until you can search for a game again and voila - all sorted.