Failed to install karbor-dashboard in devstack

[Eric Xie]

Description
===========
When i used `devstack` to install karbor-dashboard, it failed.

Steps to reproduce
==================
* Clone latest devstack
* Use devstack/local.conf.sample as local.conf in env
* Execute ./stack.sh

Expected result
===============
Installed successfully

Actual result
=============
It failed.

Environment
===========
1. devstack version
$ git log
commit 614cab33c40159f0bc10d92c9f8dc3f9783708d9
Merge: b5841fa 0b45e2f
Author: Zuul <email address hidden>
Date: Sun Jan 21 22:08:24 2018 +0000

    Merge "Remove hack for ubuntu cloud archive"

2. karbor-dashboard version
$ git log
commit 761570ef879603188e546bc324ea883228c31114
Author: OpenStack Proposal Bot <email address hidden>
Date: Wed Dec 13 07:08:52 2017 +0000

    Imported Translations from Zanata

    For more information about this automatic import see:
    https://docs.openstack.org/i18n/latest/reviewing-translation-import.html

    Change-Id: I51824947b49b97d592e080d66efea4538a248aa9

Logs
==============
2018-01-22 06:23:50.182 | Could not satisfy constraints for 'horizon': installation from path or url cannot be constrained to a version

[Eric Xie (eric-xie)]

Same as bug https://bugs.launchpad.net/devstack/+bug/1540328.

It works when i use `git reset --hard` on /opt/stack/requirements.