When there are merge requests in the same project that have their
source/target branches to each other and collaboration is allowed,
it can result to an infinite loop when a Reporter/Guest views a
project.

This fix adds a `skip_collaboration_check` to `Gitlab::UserAccess`
so when `Project#fetch_branch_allows_collaboration` calls
`MergeRequest#can_be_merged_by?` (which calls `Gitlab::UserAccess`
again), it will not check if collaboration is allowed.