Change the method of checking if a lport is configured SG in SGApp
Change the method of checking if a lport is configured SG in SGApp

Because the SG default value in a lport was changed to a empty list,
SGApp should use 'not secgroups' rather than 'secgroups is None' to
check if this lport is configured SG.

Change-Id: Ifc58fc87cdb56e2fc011a0af0689dc8c61b26cfd
Closes-bug: #1613993

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow