Keep old behavior of setuptools for editable installs
Keep old behavior of setuptools for editable installs

In the 25.0.0 release [1] of setuptools during any install
operation the package in not overwritten. If a package is
installed from another requirement via pip and then it is
installed again from git, it is not updated causing
check_libs_from_git to fail.

[1] https://setuptools.readthedocs.io/en/latest/history.html#v25-0-0

Change-Id: Ibaa1d4157816ea649f4452756fbde25951347001
Closes-Bug: #1605998

bswartz/devstack,group-policy/devstack,richliu/devstack,nawawi/openstack,noironetworks/devstack,openstack-dev/devstack,nawawi/openstack,noironetworks/devstack,openstack-dev/devstack,dtroyer/devstack,richliu/devstack,group-policy/devstack,dtroyer/devstack,bswartz/devstack