Remove secgroups related methods

As tempest.scenario.manager was announced stable interface in Tempest 27.0.0[1]
it can be now reused in plugins.

Barbican tempest plugin still uses nova-network old interface for floating ip
related methods, this patch removes them and use tempests's ones which
already use neutron's interface.[2]

Replaced/Removed methods:
    * _default_security_group
    * _create_security_group
    * _create_loginable_secgroup_rule
    * _create_security_group_rule

Etherpad concerning this effort:
https://etherpad.opendev.org/p/tempest-scenario-manager-cleanup

[1] https://docs.openstack.org/releasenotes/tempest/v27.0.0.html#release-notes-27-0-0
[2] https://opendev.org/openstack/tempest/commit/bbc9dd34f6455aa7fdd70737764408e48c1494f8

Change-Id: I7605fe11caa8ae5725e0c0583c623ebad73d40da
3 files changed