Fix Instance secgroup update error with Nova secgroup

Nova add/remove_security_group takes secgroup name instead of id.
Add api test for update_instance_security_group in api.nova.

Change the parameter name "new_sgs" of server_update_security_groups
to "new_security_group_ids" to clarify it takes ID as a parameter.

Based on the initial patch in https://review.openstack.org/#/c/39940

Change-Id: I8d9b6f5c22eee5adbaea51ce352483ab74f488f6
Closes-Bug: #1207184
Merge "Fix Instance secgroup update error with Nova secgroup"