merge request timeout (502) - meta issue

There are quite a few open issues describing timeouts when creating or viewing merge request. Some of them are very old. Probably there are duplicates and maybe some of them already fixed. I'm making a list here to find them more easily. Maybe someone with more insight than me can have a quick look trough them.

• https://gitlab.com/gitlab-org/gitlab-ce/issues/1510
• https://gitlab.com/gitlab-org/gitlab-ce/issues/1661
• https://gitlab.com/gitlab-org/gitlab-ce/issues/2529
• https://gitlab.com/gitlab-org/gitlab-ce/issues/3603
• https://gitlab.com/gitlab-org/gitlab-ce/issues/3935
• https://gitlab.com/gitlab-org/gitlab-ce/issues/5960
• https://gitlab.com/gitlab-org/gitlab-ce/issues/13912
• https://gitlab.com/gitlab-org/gitlab-ce/issues/14263
• https://gitlab.com/gitlab-org/gitlab-ce/issues/14265
• https://gitlab.com/gitlab-org/gitlab-ce/issues/14312
• https://gitlab.com/gitlab-org/gitlab-ce/issues/18070
• https://gitlab.com/gitlab-org/gitlab-ce/issues/19074
• https://gitlab.com/gitlab-org/gitlab-ce/issues/19465

cc @connorshea because you are the master of issues 😉