Fix hardcoded manifest

Change-Id: I7ed50c645ba33ec9ba73e54ffe6ca3643144d887
diff --git a/scripts/cord-in-a-box.sh b/scripts/cord-in-a-box.sh
index 593de34..62f5995 100755
--- a/scripts/cord-in-a-box.sh
+++ b/scripts/cord-in-a-box.sh
@@ -111,7 +111,7 @@
     dig +short gerrit.opencord.org || (echo "ERROR: gerrit.opencord.org can't be looked up in DNS" && exit 1)
 
     mkdir $CORDDIR && cd $CORDDIR
-    repo init -u https://gerrit.opencord.org/manifest -b master -g build,onos,orchestration,voltha
+    repo init -u https://gerrit.opencord.org/manifest -b $REPO_BRANCH -g build,onos,orchestration,voltha
     repo sync
 
     # check out gerrit branches using repo