Always assume glance is uwsgi mode for grenade

Since older devstack versions do not support glance
in standalone mode, make grenade configure the base
and target for glance deployed with uwsgi.

It is failing in legacy grenade jobs[1], for devstack based
jobs it is taken care in https://review.opendev.org/#/c/741479/2

[1] http://lists.openstack.org/pipermail/openstack-discuss/2020-July/016006.html

Change-Id: Ic84b2e5a2f3677156f6ddb523b9dc91abeda992b

devstack-vm-gate.sh

@@ -531,6 +531,7 @@ function setup_localrc {
             localrc_set "$localrc_file" "GRENADE_PHASE" "target"
         fi
         localrc_set "$localrc_file" "CEILOMETER_USE_MOD_WSGI" "False"
+        localrc_set "$localrc_file" "GLANCE_STANDALONE" "False"
     fi
 
     if [[ "$DEVSTACK_GATE_TEMPEST_LARGE_OPS" -eq "1" ]]; then