don't explicitly delete security group rules
don't explicitly delete security group rules

security group rules will get deleted when the security group is
deleted. Doing deletes ourselves in tempest adds complexity, pushes
load at neutron, and slows things down for not particularly
interesting reason.

Change-Id: I6bac772d8e50f6e7174b267dbf55670b6bf891d7

zsoltdudas/lis-tempest,Tesora/tesora-tempest,Juniper/tempest,LIS/lis-tempest,openstack/tempest,vedujoshi/tempest,masayukig/tempest,Tesora/tesora-tempest,openstack/tempest,LIS/lis-tempest,sebrandon1/tempest,vedujoshi/tempest,zsoltdudas/lis-tempest,sebrandon1/tempest,Juniper/tempest,bigswitch/tempest,bigswitch/tempest,cisco-openstack/tempest,cisco-openstack/tempest,masayukig/tempest