Add --security-group option to port-create

[Usage] quantum port-create --security-group sg1 --security-group sg2 net1
A security group can be specified by name.

Part of blueprint quantum-client-security-groups

Change-Id: I82126f4839c4c0b265912ac6f5e111f5fbd2f72b
Merge "Add --security-group option to port-create"