tests: Increase time limit to 120 seconds

The "test launching client on a specific screen" suit is very slow.

However, it is also necessary to avoid issues such as #1069 or #154
from regressing again.

This is a temporary fix until a faster test client "daemon" is
developped.

tests/run.sh

@@ -194,7 +194,7 @@ start_awesome() {
 # Count errors.
 errors=0
 # Seconds after when awesome gets killed.
-timeout_stale=60
+timeout_stale=120 # FIXME This should be no more than 60s
 
 for f in $tests; do
     echo "== Running $f =="