Fix race condition with UpdateMirrorWorker Lease

Merged Paco Guzman requested to merge 748-update-mirror into master

Any time we modify the project import state to an in progress we're going to execute the sidekiq job not lease to try to obtain in this workflow. This fixes the UI problem when an user try to update a mirror just inside a lease timeout.

Closes #748 (closed)

/cc @jacobvosmaer-gitlab @stanhu