Bump Gerrit to v3.4.1 in docker tests

Change-Id: I872c87695e9276208943b3236031bbc6703de177

src/test/docker/gerrit/Dockerfile

diff --git a/src/test/docker/gerrit/Dockerfile b/src/test/docker/gerrit/Dockerfile
index 7269a3a..6834f57 100644
--- a/src/test/docker/gerrit/Dockerfile
+++ b/src/test/docker/gerrit/Dockerfile
@@ -1,6 +1,6 @@
-FROM gerritcodereview/gerrit:3.3.7 
+FROM gerritcodereview/gerrit:3.4.1
 
-ENV GERRIT_BRANCH=stable-3.3
+ENV GERRIT_BRANCH=stable-3.4
 
 ENV GERRIT_CI_URL=https://gerrit-ci.gerritforge.com/job