Instead, use the common_settings file to source all the variables
we need at the early stages of devstack setup and during the upgrade
itself. This also fixes an issue with the networking-generic-switch
upgrade script, which is run from the old release instead of the new
one.
It depends on a patch from an older release, as grenade is setup
using settings from an older release, we need common_setting to be
populated there.
Change-Id: I0d6d3e9e60785bb9b6a10c8c7a07867a5b2a5e6e
Depends-On: I34fb68c150b753824bd2687a1f522ac87771a5e3
c4b39e7b09