tests: test-cookie-invalidation add a time wait after client termination

That ensures that the client is already terminated when the final check
starts.

tests/test-cookie-invalidation

@@ -73,6 +73,7 @@ if test $? != 0;then
 fi
 
 rm -f "${PIDFILE2}"
+sleep 3
 
 echo "Proper termination and connecting again with same (invalidated) cookie... "
 #( echo "test" | $OPENCONNECT -q localhost:$PORT -u test -C "$COOKIE" --servercert=d66b507ae074d03b02eafca40d35f87dd81049d3 --cookieonly >/dev/null 2>&1 ) ||