grenade assumes definitions like neutron_plugin_configure_common are
available just by sourcing lib/neutron-legacy.
it's ok for ml2 because lib/neutron-legacy sources lib/neutron_plugins/$Q_PLUGIN if available.
however, it isn't true for decomposed neutron plugins as they don't have the $Q_PLUGIN file in devstack tree.
grenade assumes definitions like neutron_ plugin_ configure_ common are plugins/ $Q_PLUGIN if available.
available just by sourcing lib/neutron-legacy.
it's ok for ml2 because lib/neutron-legacy sources lib/neutron_
however, it isn't true for decomposed neutron plugins as they don't have the $Q_PLUGIN file in devstack tree.