Increase time limit of bcast2 and bcast3 to 12mins.

Timeout is reported on some overloaded machines with 10 minutes time
limitation.
Signed-off-by: Xin Zhao <xinzhao3@illinois.edu>

test/mpi/coll/testlist

@@ -35,8 +35,8 @@ bcasttest 10
 bcast2 4
 # More that 8 processes are required to get bcast to switch to the long
 # msg algorithm (see coll definitions in mpiimpl.h)
-bcast2 10 timeLimit=600
-bcast3 10 timeLimit=600
+bcast2 10 timeLimit=720
+bcast3 10 timeLimit=720
 bcastzerotype 1
 bcastzerotype 4
 bcastzerotype 5