Bump bazel version for the master branch up to 0.27.0

Change-Id: I8c8f863a47e51f73d761b08824a12db308d2e08b
diff --git a/jjb/onos/install-bazel.sh b/jjb/onos/install-bazel.sh
index f805e4a..7f9b727 100644
--- a/jjb/onos/install-bazel.sh
+++ b/jjb/onos/install-bazel.sh
@@ -7,7 +7,11 @@
 then
     BAZEL_VERSION="0.19.2"
 else
-    BAZEL_VERSION="0.24.1"
+    if [ ${GERRIT_BRANCH} == "master" ]; then
+        BAZEL_VERSION="0.27.0"
+    else
+        BAZEL_VERSION="0.24.1"
+    fi
 fi
 
 if [ ${BAZEL_VERSION} != "none" ]