Fix Ansible bootstrap upper constraint use
Fix Ansible bootstrap upper constraint use

When bootstrapping the Ansible runtime venv the version of
pip in the initial venv might be old and unable to understand
the --constraint option.

This patch ensures that the pip, setuptools and wheel upgrade
does not try to use the --constraint option (they're fixed pins
anyway so it's not needed) and then applies the --constraint
option once we know we're at the right version of pip.

Change-Id: Ic482493c800362b896bfe5083b253f1d33d809b5

yanyao/openstack-ansible,bunchc/openstack-ansible,openstack/openstack-ansible,os-cloud/os-ansible-deployment,bunchc/openstack-ansible,robb-romans/openstack-ansible,weezer/openstack-ansible,BjoernT/openstack-ansible,cfarquhar/openstack-ansible,Logan2211/openstack-ansible,BjoernT/openstack-ansible,BjoernT/os-ansible-deployment,Logan2211/openstack-ansible,cfarquhar/openstack-ansible,cloudnull/os-ansible-deployment,openstack/openstack-ansible,BjoernT/os-ansible-deployment,robb-romans/openstack-ansible,yanyao/openstack-ansible,os-cloud/os-ansible-deployment,stackforge/os-ansible-deployment,stackforge/os-ansible-deployment,cloudnull/os-ansible-deployment,weezer/openstack-ansible,BjoernT/os-ansible-deployment