Add --security-group option to port-update

port-update --security_groups list=true ... is not user-friendly.

bug 1161078

This commit also changes the followings:
- Add --no-security-groups options to port-create for consistency.
- Make --security-group and --no-security-groups mutual-exclusive
  to prevent both options specified at the same time.

Change-Id: Ibfe165a0cbdfb0eb582784c80a3371de33108fdb
Merge "Add --security-group option to port-update"