Make all future skipped builds as processable when retrying a build

## What does this MR do?

Makes a builds that are marked as skipped when a pipeline is processed to be reprocessed by changing their's state to created.

## Why was this MR needed?

Currently retry is broken. When you retry a build of pipeline it will succeed and be marked as succeeded, when the next stages should be triggered.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21066

See merge request !5879