Updated documentation of return values and added test to verify
return values
Function self.conn.search_security_groups() cannot be used here.
Arguments for filtering such as 'description' would have to be passed
to self.conn.search_security_groups() in its 'filters' argument [1].
The latter is passed to both as query arguments to OpenStack API
and later to _utils._filter_list() [2] for filtering the results.
Some arguments such as 'any_tags' are only used as query arguments
by openstacksdk [3] when querying OpenStack API. They are no valid
attributes in security_group.py [4]. Whenever those non-attribute
arguments are passed to self.conn.search_security_groups(),
_utils._filter_list() [2] would drop all results because no result
would have a matching attributes.
[1] 0898398415/openstack/cloud/_security_group.py (L31)
[2] 0898398415/openstack/cloud/_utils.py (L63)
[3] 0898398415/openstack/common/tag.py (L19)
[4] 0898398415/openstack/network/v2/security_group.py
Change-Id: Ie7fe9d2e973d38751c48e71e6bd55e56a591ac1f
