Allow sress test runner to skip based on available services

Also add run network connectivity start/stop test as stress.

Change-Id: I3441d1deb7804033f73441a626e9cb8ae632501a
diff --git a/tempest/stress/driver.py b/tempest/stress/driver.py
index e007a49..0b3ac8f 100644
--- a/tempest/stress/driver.py
+++ b/tempest/stress/driver.py
@@ -132,7 +132,14 @@
         computes = _get_compute_nodes(controller, ssh_user, ssh_key)
         for node in computes:
             do_ssh("rm -f %s" % logfiles, node, ssh_user, ssh_key)
+    skip = False
     for test in tests:
+        for service in test.get('required_services', []):
+            if not CONF.service_available.get(service):
+                skip = True
+                break
+        if skip:
+            break
         if test.get('use_admin', False):
             manager = admin_manager
         else: