When bulk ports are created with a security group supplied, the
resulting port(s) should only have that security group assigned. But the
resulting ports are getting both the requested security group as well as
the tenant default security group assigned. This fixes that condition.
In order to ensure that bulk port creation results in the proper
assignment of security groups, add some testing.
Change-Id: I65aca7cd14447cc988e4bc4ab62bc7b9279e7522
Fixes-Bug: #1842666