Docs: Clarify that for external groups the name in GroupInfo can be missing
Docs: Clarify that for external groups the name in GroupInfo can be missing

For external groups the group name is missing if there is no group
backend that can resolve the group UUID. E.g. this can happen when a
plugin that provided a group backend was uninstalled (e.g. the
singleusergroup plugin).

Change-Id: I0d7f7253698c0125d7692781fa32f4294cda3bcc
Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
(cherry picked from commit 219e797144d7e6425373bd35c7fa1f48b8ac4abb)

qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,GerritCodeReview/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,WANdisco/gerrit,WANdisco/gerrit,WANdisco/gerrit,GerritCodeReview/gerrit,qtproject/qtqa-gerrit,WANdisco/gerrit