Fix GERRIT_VERSION to GERRIT_BRANCH rename lost in merge I0285d2c7

Change-Id: Ic48fd37261173331faeb3a2ce460aa778ffea3dd
diff --git a/src/test/docker/gerrit/Dockerfile b/src/test/docker/gerrit/Dockerfile
index f5f7bf5..02c3af1 100644
--- a/src/test/docker/gerrit/Dockerfile
+++ b/src/test/docker/gerrit/Dockerfile
@@ -11,7 +11,7 @@
     nfs-utils \
     && yum -y clean all
 
-ENV GERRIT_VERSION master
+ENV GERRIT_BRANCH master
 
 # Add gerrit user
 RUN adduser -p -m --uid 1000 gerrit --home-dir /home/gerrit