Doc multi_instance_display_name_template option

fixes bug 1128544

multi_instance_display_name_template is a new option to grizzly,
which this patch documents

unrelated to the bug report, security_group_api was missing, so
this was added too

patch2 clarifies wording

Change-Id: I0cf9615bdc1cda0aaae0bf383f5d598d9b41c543
Merge "Doc multi_instance_display_name_template option"