Fixed #1952 docker ssh connection times can be slow when UseDNS is enabled

CHANGELOG

@@ -12,6 +12,7 @@ v 8.0.0 (unreleased)
   - Search for comments should be case insensetive
   - Create cross-reference for closing references on commits pushed to non-default branches (Maël Valais)
   - Ability to search milestones
+  - Disabled DNS lookups for SSH in docker image (Rowan Wookey)
 
 v 7.14.1 (unreleased)
   - Only include base URL in OmniAuth full_host parameter (Stan Hu)

docker/Dockerfile

@@ -25,6 +25,9 @@ RUN mkdir -p /opt/gitlab/sv/sshd/supervise \
     && ln -s /opt/gitlab/sv/sshd /opt/gitlab/service \
     && mkdir -p /var/run/sshd
 
+# Disabling use DNS in ssh since it tends to slow connecting
+RUN echo "UseDNS no" >> /etc/ssh/sshd_config
+
 # Prepare default configuration
 RUN ( \
   echo "" && \