Try to make system tests more reliable

• Most system tests that fail do so because of a Ferrum::DeadBrowserError, which happens when the received response is truncated. Doubling the websocket limit may help?
  • Nope
• Try to increase the memory limits of the runners on xuan. Not sure what is the default value for memory
  • . Disabled oom_kill_disable to see if it changes anything? Nope
  • Set an (arbitrary) large value
• Run the system tests on gitlab.org to see if it changes anything Les tests échouent tous sur Request to https://runner-xs6vzpvo-project-24458983-concurrent-0:35127/users/sign_in failed to reach server, check DNS and server status. Mmmm
• Upgrade the gitlab-runner version
• Disable the external map tiles (it's slow and unpredictable)
• Disable JS requests to external servers entirely (like we do server-side)