lib/tempest: remove the allow_port_security_disabled option
lib/tempest: remove the allow_port_security_disabled option

Now that Liberty is EOLed, the feature flag is not needed anymore.

Change-Id: I5206535761773d4bcb02ebb8f25d1b0c1b59110c
Depends-On: If0b2168080a0b0ecdc6682ef69856a0879f4f6d3

bswartz/devstack,richliu/devstack,openstack-dev/devstack,group-policy/devstack,openstack-dev/devstack,noironetworks/devstack,richliu/devstack,group-policy/devstack,nawawi/openstack,noironetworks/devstack,bswartz/devstack,dtroyer/devstack,dtroyer/devstack,nawawi/openstack