Bug 1279616

Description of problem:
openstack overcloud update stack should be run with -i (interactive) to pause on breakpoints. The issue is that it's quite confusing what breakpoint you're actually clearing when prompted.

Here's some sample output during the update:

[stack@instack ~]$ openstack overcloud update stack overcloud -i --templates templates-y1 -e templates-y1/overcl
oud-resource-registry-puppet.yaml -e templates-y1/environments/network-isolation.yaml -e templates-y1/environmen
ts/net-single-nic-with-vlans.yaml -e custom-environment-7.1.yaml -e /home/stack/update.yaml                     
starting package update on stack overcloud
IN_PROGRESS
<snip>
IN_PROGRESS
WAITING
not_started: [u'overcloud-compute-0', u'overcloud-controller-0', u'overcloud-controller-1', u'overcloud-controller-2']
on_breakpoint: [u'overcloud-cephstorage-0']
Breakpoint reached, continue? Regexp or Enter=proceed, no=cancel update, C-c=quit interactive mode: 
removing breakpoint on overcloud-cephstorage-0
IN_PROGRESS
<snip>
IN_PROGRESS
WAITING
completed: [u'overcloud-cephstorage-0']
on_breakpoint: [u'overcloud-compute-0', u'overcloud-controller-0', u'overcloud-controller-1', u'overcloud-controller-2']
Breakpoint reached, continue? Regexp or Enter=proceed, no=cancel update, C-c=quit interactive mode: 
removing breakpoint on overcloud-controller-2
IN_PROGRESS
<snip>
IN_PROGRESS
WAITING
completed: [u'overcloud-cephstorage-0', u'overcloud-controller-2']
on_breakpoint: [u'overcloud-controller-0', u'overcloud-controller-1', u'overcloud-compute-0']
Breakpoint reached, continue? Regexp or Enter=proceed, no=cancel update, C-c=quit interactive mode: 
removing breakpoint on overcloud-compute-0
IN_PROGRESS
IN_PROGRESS
IN_PROGRESS


The first time you are prompted, there is only one breakpoint in the list: overcloud-cephstorage-0'
It's obvious what will be cleared when you press Enter.

Now consider the next 2 prompts:

completed: [u'overcloud-cephstorage-0']
on_breakpoint: [u'overcloud-compute-0', u'overcloud-controller-0', u'overcloud-controller-1', u'overcloud-controller-2']
Breakpoint reached, continue? Regexp or Enter=proceed, no=cancel update, C-c=quit interactive mode: 
removing breakpoint on overcloud-controller-2

and

completed: [u'overcloud-cephstorage-0', u'overcloud-controller-2']
on_breakpoint: [u'overcloud-controller-0', u'overcloud-controller-1', u'overcloud-compute-0']
Breakpoint reached, continue? Regexp or Enter=proceed, no=cancel update, C-c=quit interactive mode: 
removing breakpoint on overcloud-compute-0

Note that in both cases when I pressed Enter, the last breakpoint in the list was cleared. This may be as designed, but is very confusing. There's no way we could expect anyone to know that.

Also, what is "Regexp" prompting the user to do?