Switch back to nc in test_load_balancer_basic

After test_load_balancer_basic started using inetd instead of netcat
we've started getting "BadStatusLine" errors from urllib.

That is why we need to move back to using netcat.
Also handle "BadStatusLine" error.

Related bug: 1309252
Change-Id: Ida919c63e27c6a003be4c249ba2e6f3e2ea7a7b3
Relax security group rules cleanup

Security groups rules are automatically deleted when we delete the
security group so this is not really necessary, besides that,
nova-network doesn't provide a way to get current status of a rule
(a proof of concept here https://review.openstack.org/#/c/85725/) which
means that we never know if it is really deleted.
Currently it works cause we don't really check the timeouts, but a the
next patch of this series - https://review.openstack.org/#/c/82709/ will
and depends on this to work.

Change-Id: If82d1727b2c5f752e48a2da2c8a029e346f3593e
Upload public image requires admin role by default

In glance the previous default was that any tenant could upload an
image as public which is likely not the desired default. This patch
changes the tempest tests so that images are no longer uploaded as
is_public=True by normal tenants so the policy change can merge in glance.

Glance change: https://review.openstack.org/#/c/92739/

Change-Id: If6a3aa0f7317b628b81b51d82108a18c701a1fd5
Merge "Upload public image requires admin role by default"
Merge "Relax security group rules cleanup"
Merge "Switch back to nc in test_load_balancer_basic"
Merge branch 'master' of https://github.com/openstack/tempest