Refresh systems index after modification through API

Addresses:

  katello system register --name system --org=org --environment env
  katello system info --name=system --org=org
  Could not find System [ system ] in Org [ org ]

The problem was the elastic search was not updated before searching
for the newly created system.
Refresh system groups index after modification through API

The problem was the elastic search was not updated before searching
for the newly created system group.
Fix unit tests for refreshing system and system_group indexes in API
Merge pull request #2585 from iNecas/system-register-es-refresh

Refresh systems index after modification through API