Add missing --test_env prefix for Bazel test variable

Fix the DOCKER_HOST variable as argument to the Bazel tests
with --test_env parameter.

Change-Id: If682fe4a23b562ab680fdd908408dbed41f1b771
diff --git a/jenkins/gerrit-bazel-test.sh b/jenkins/gerrit-bazel-test.sh
index 7538554..0beb6c2 100755
--- a/jenkins/gerrit-bazel-test.sh
+++ b/jenkins/gerrit-bazel-test.sh
@@ -9,7 +9,7 @@
                    --test_verbose_timeout_warnings --build_tests_only \
                    --test_timeout 3600 \
                    --test_tag_filters=-flaky,-docker \
-                   DOCKER_HOST=$DOCKER_HOST"
+                   --test_env DOCKER_HOST=$DOCKER_HOST"
 
 if [ "{branch}" == "stable-2.16" ] || [ "{branch}" == "stable-2.15" ] || [ "{branch}" == "stable-2.14" ]
 then