Don't require passing in port_security=False if security_groups present

If creating a port on a network that is marked as port_security_enabled=False
and one passes in a security_group in the port_create request previously an
error was raised saying they needed to also pass in
port_security_enabled=False. This patch removes that requirement and instead
sets port_security_enabled=True internally if a port has an ip_address and a
security_group is passed in. This is more convient and does not break
backwards compatibility.

Closes-bug: #1267249
Change-Id: Ifb5a5511f016a5d8c5b5075c9fdc27279cdd9bb5
Merge "Don't require passing in port_security=False if security_groups present"