Add Constraints support

Adding constraints support to clients is slightly more complex than
services as the clients themselves are listed in upper-constraints.txt
which leads to errors that you can't install a specific version and a
constrained version.

This change adds constraints support by also adding a helper script to
edit the constraints to remove tripleo-common.

Change-Id: I773849a84014203366e88432e2cad57b6685065e

tox.ini

@@ -5,9 +5,10 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+install_command = {toxinidir}/tools/tox_install.sh {env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
+   CLIENT_NAME=tripleo-common
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
 commands = python setup.py test --slowest --testr-args='{posargs}'