Improved specs

Fixed non-fast-forward fetch

Will git fetch with "--prune"

(temporarily disabling any operations to anex as it's currently not
replicated)

Try not to loose data when REST requests fail

[ES] More accurate as_indexed_json

fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/349

It makes database indexer stable to corrupted data in database.

/cc @jnijhof 

See merge request !244