Update currentTime in dispatch loop

A request, like input device grabs, may check a request timestamp
against currentTime. It is possible for currentTime to lag a previously
sent event timestamp. If the client makes a request based on such an
event timestamp, the request may fail the validity check against
currentTime unless we always update the time before processing the
request.

Signed-off-by: Chase Douglas <chase.douglas@canonical.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit 312910b4e3)

dix/dispatch.c

@@ -393,6 +393,9 @@ Dispatch(void)
                 }
                 /* now, finally, deal with client requests */
 
+                /* Update currentTime so request time checks, such as for input
+                 * device grabs, are calculated correctly */
+                UpdateCurrentTimeIf();
                 result = ReadRequestFromClient(client);
                 if (result <= 0) {
                     if (result < 0)