tests: replace start-stop-daemon with async action

test/integration/roles/test_uri/handlers/main.yml

----
-- name: stop SimpleHTTPServer
-  shell: start-stop-daemon --stop --pidfile {{ output_dir }}/SimpleHTTPServer.pid --exec {{ py2.stdout }}

test/integration/roles/test_uri/tasks/main.yml

@@ -27,8 +27,9 @@
   register: py2
 
 - name: start SimpleHTTPServer
-  shell: start-stop-daemon --start --pidfile {{ output_dir }}/SimpleHTTPServer.pid --background --make-pidfile --chdir {{ files_dir }} --exec {{ py2.stdout }} -- -m SimpleHTTPServer {{ http_port }}
-  notify: stop SimpleHTTPServer
+  shell: cd {{ files_dir }} && {{ py2.stdout }} -m SimpleHTTPServer {{ http_port }}
+  async: 15 # this test set takes ~8 seconds to run
+  poll: 0
 
 - wait_for: port={{ http_port }}