Fix an error where we were unable to create a CommitStatus for running state

Due to severe refactoring of Pipeline we introduced regression in how CommitStatus is handled. We received an report that it's impossible to create a CommitStatus with state `running` when there were not previous status. 

The support for Commit Statuses should be simplified. Right now I'm doing minimal change to move forward and fix a bug, but I'll create a new MR that will move all logic that is now part of `lib/api/commit_statuses.rb` to separate service to simplify the implementation.

This error happens due to the fact that we introduced additional status of builds: `created`.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21345

See merge request !6107