correct the behavior of 'security_groups=[]' for OS::Neutron::Port resource creation

[huangtianhua]

The behaviors of neutron port-create api with security_groups=[] and without security_groups are different:
1. with security_groups=[], the port will be created without securityGroup
2. without security_groups, the port will be created in 'default' securityGroup

Now in heat, the OS::Neutron::Port resource, change the behavior of the case 1, need to correct this.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/121794

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/121794
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=8239b3f655a3ac3c63888b0df6f143d7ff50512a
Submitter: Jenkins
Branch: master

commit 8239b3f655a3ac3c63888b0df6f143d7ff50512a
Author: huangtianhua <email address hidden>
Date: Tue Sep 16 17:45:29 2014 +0800

    Pass correct 'security_groups' value for port operations

    Make sure pass the correct value of 'security_groups'
    property to neutronClient for OS::Neutron::Port resource
    operations.

    Change-Id: I84fa2c149c18b0b85be7cf1ff5a8ab2641a5c276
    Closes-bug: #1369933