bug20222: racier test

Add a SLEEP to the keepalive test in TEST-CLIENT to give the server
time to close the connection if it doesn't honour the keep-alive
request.

Much easier to reproduce bug20222 this way.

Change-Id: Ia8f4bb9ad51be33f4a17c5cc122c8b1ef4a24320

test/t-aserve.cl

@@ -1406,6 +1406,10 @@
       (test t (and "with no-keepalive" (not (null socket))))
 
       ; now reuse it
+
+      ;; bug20222: give a chance for the server to close the
+      ;; connection
+      (sleep (random 1.0))
       (multiple-value-bind (body code3 headers uri socket2)
 	  (x-do-http-request (format nil "~a/redir-target" prefix-local)
 			     :keep-alive t