Support Tempest test as gate job

Now Zaqar isn't using Tempest for jenkins gate checking, which is
a missing. This patch fixes it by using Tempest's all-plugin to
run Zaqar's Tempest cases in tree.

Change-Id: I7e10a5b218b60eea47a96d36ebeb4029d33e7edd

devstack/gate/gate_hook.sh

@@ -39,6 +39,10 @@ function run_devstack_gate() {
 function run_tempest_tests() {
     export DEVSTACK_GATE_TEMPEST=1
     run_devstack_gate
+
+    cd $BASE/new/tempest/
+    sudo -E testr init
+    sudo -E tox -eall-plugin zaqar
 }
 
 function run_zaqarclient_tests() {