Use gate_hook to enable q-trunk for rally.

Instead of making devstack enable it, because it can have
undesired effects for other rally-using gate jobs.
(See Closes-Bug for an example)

Closes-Bug: #1643451

(cherry picked from commit b1405cbe1e)
Change-Id: Id971432955196a7d5f64c598aeebf1a7bc245321

devstack/lib/rally

@@ -1,13 +0,0 @@
-#!/bin/bash
-
-RALLY_EXTRA_DIR="$DEST/neutron/rally-jobs/extra"
-
-# If rally has been configured, .setup files can be sourced to control the
-# neutron configuration required to run the scenario plugins.
-if [[ "$DEVSTACK_PLUGINS" =~ "rally" ]];
-then
-    for file in $(ls $RALLY_EXTRA_DIR/*.setup);
-    do
-        source $file
-    done
-fi

devstack/plugin.sh

@@ -7,7 +7,6 @@ source $LIBDIR/l2_agent_sriovnicswitch
 source $LIBDIR/ml2
 source $LIBDIR/qos
 source $LIBDIR/ovs
-source $LIBDIR/rally
 source $LIBDIR/trunk
 
 Q_BUILD_OVS_FROM_GIT=$(trueorfalse False Q_BUILD_OVS_FROM_GIT)

neutron/tests/contrib/gate_hook.sh

@@ -9,6 +9,7 @@ NEUTRON_PATH=$GATE_DEST/neutron
 GATE_HOOKS=$NEUTRON_PATH/neutron/tests/contrib/hooks
 DEVSTACK_PATH=$GATE_DEST/devstack
 LOCAL_CONF=$DEVSTACK_PATH/local.conf
+RALLY_EXTRA_DIR=$NEUTRON_PATH/rally-jobs/extra
 
 
 # Inject config from hook into localrc
@@ -29,6 +30,18 @@ function load_conf_hook {
 }
 
 
+# Tweak gate configuration for our rally scenarios
+function load_rc_for_rally {
+    for file in $(ls $RALLY_EXTRA_DIR/*.setup); do
+        local config=$(cat $file)
+        export DEVSTACK_LOCAL_CONFIG+="
+# generated from hook '$file'
+${config}
+"
+    done
+}
+
+
 case $VENV in
 "dsvm-functional"|"dsvm-fullstack")
     # The following need to be set before sourcing
@@ -78,8 +91,7 @@ case $VENV in
     ;;
 
 "rally")
-    # NOTE(yamamoto): This is a no-op placeholder to allow
-    # further changes.
+    load_rc_for_rally
     $BASE/new/devstack-gate/devstack-vm-gate.sh
     ;;