Add ability to specify branch when creating graphs

- This is useful if we don't control what version is deployed from the
  test

Change-Id: I25e39480538d76b73664cdcf2c49f3770eeb9bc3
(cherry picked from commit dd5ca963c429dbaac0664e60344f05cf9e8ec038)
diff --git a/TestON/tests/USECASE/SegmentRouting/SRBridging/SRBridging.params.tofino b/TestON/tests/USECASE/SegmentRouting/SRBridging/SRBridging.params.tofino
index 7442bf4..88d669b 100644
--- a/TestON/tests/USECASE/SegmentRouting/SRBridging/SRBridging.params.tofino
+++ b/TestON/tests/USECASE/SegmentRouting/SRBridging/SRBridging.params.tofino
@@ -5,6 +5,7 @@
         <nodeCluster>Fabric</nodeCluster>
         <builds>20</builds>
         <jobName>SRBridging-tofino</jobName>
+        <branch>master</branch>
     </GRAPH>
 
     <SCALE>