Save only valid record in service migrations

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'better-service-migration' into 'master'

Better service migration

Prevent crashes and saving invalid record. Skip non-valid services.

Better fix for https://github.com/gitlabhq/gitlabhq/pull/8199

See merge request !1235