Increase timeouts for Gitaly RPCs

This change increases the timeout of the following RPCs in Sidekiq from
55 seconds to 6 hours:

* CreateFork
* CreateRepositoryFromUrl
* FetchSourceBranch

Prior to https://gitlab.com/gitlab-org/gitlab/merge_requests/16926,
`default_timeout` was unlimited for Sidekiq jobs, but now it is 55
seconds. However, the above RPCs can take a long time to run.

To avoid timing out prematurely, we increase these values to long timeouts
to ensure that they can complete.

Closes https://gitlab.com/gitlab-com/gl-infra/production/issues/1187

lib/gitlab/gitaly_client/repository_service.rb

@@ -123,7 +123,7 @@ module Gitlab
           :create_fork,
           request,
           remote_storage: source_repository.storage,
-          timeout: GitalyClient.default_timeout
+          timeout: GitalyClient.long_timeout
         )
       end
 
@@ -138,7 +138,7 @@ module Gitlab
           :repository_service,
           :create_repository_from_url,
           request,
-          timeout: GitalyClient.default_timeout
+          timeout: GitalyClient.long_timeout
         )
       end
 
@@ -189,7 +189,7 @@ module Gitlab
           :repository_service,
           :fetch_source_branch,
           request,
-          timeout: GitalyClient.default_timeout,
+          timeout: GitalyClient.long_timeout,
           remote_storage: source_repository.storage
         )