Web/System hooks not retried if remote server returns non-200 error code.

Created by: bladealslayer

It seems that executing Web and System hooks ignores the return code of the remote server. As a result a hook calls with return code 4xx or 5xx from the remote server are considered successful and not retried.

See https://github.com/gitlabhq/gitlabhq/blob/master/app/models/web_hook.rb#L31.

Perhaps if the return code should be checked and exception raised on non-200 return code?

I can submit a PR, if you think this is the right way to go, @randx.