removed deprecated parameter --public

As noted by bcwaldon the parameter can be removed after updating
Devstack. Should be done after merging the following change:

https://review.openstack.org/#/c/39323/

Change-Id: I8d0f7ab4cccccf022446374a31e03ac913cfb136
Merge "removed deprecated parameter --public"
Revert "removed deprecated parameter --public"

While trunk devstack was updated for this, stable/folsom and stable/grizzly
are not and grenade is now broken.  I'm not sure how long --public was
undocumented but it may be that certain cli args may need to remain deprecated
but supported for longer than we wish.

This reverts commit ce8636b6b3c4b606483cfb2bc405d86224f309bc

Change-Id: I91d4884e470c8fcc611dae62a30fa22d08dbec03