install LIBS_FROM_GIT using python 2 and 3 where appropriate
install LIBS_FROM_GIT using python 2 and 3 where appropriate

When installing a library from source and python 3 is enabled, first run
the installation process with python 2 enabled to ensure the library is
also installed under python 2 for any services not yet running under
3. The python 3 version is installed second so that command line tools
installed with libraries are installed under python 3 when python 3 is
enabled.

Change-Id: Ibb0f7a68d21081bf7652a0c1515080c0c54888ca
Signed-off-by: Doug Hellmann <0798ebecfb7bc4dfb9d0445c2fa030eb64e1fa1c@doughellmann.com>

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