Changed random mission selector to be more random.

changed an if to a while loop so it keeps checking if the same mission
is selected and added  give up clause to stop it looping forever if
random number was always the same. (very unlikly).
Fixed undeclared new veriables.

I just read some documentation on sqf and relised i hadent decalred my
variables.
Merge pull request #3 from jamesoneill/master

Hi fly boy just a few tweaks to the mission controllers.