Added "drivers" to cells that defined ONOS_APPS.

Change-Id: I8e7cbea037ea09504662fb17ef328b547d21050a
diff --git a/tools/test/cells/beast-3 b/tools/test/cells/beast-3
index fc58137..6586ddc 100644
--- a/tools/test/cells/beast-3
+++ b/tools/test/cells/beast-3
@@ -11,4 +11,4 @@
 export OC2=10.254.1.202
 export OC3=10.254.1.203
 
-export ONOS_APPS=null,intentperf
+export ONOS_APPS="drivers,null,intentperf"