main-loop: suppress warnings under qtest

commit 01c22f2c ("main-loop: Suppress
"I/O thread spun" warnings for qtest") doesn't actually disable the
warning for everyone since some tests don't run under the qtest
accelerator.

Check qtest_driver instead.

Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <1448882964-22433-1-git-send-email-mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

main-loop.c

@@ -230,7 +230,7 @@ static int os_host_main_loop_wait(int64_t timeout)
     if (!timeout && (spin_counter > MAX_MAIN_LOOP_SPIN)) {
         static bool notified;
 
-        if (!notified && !qtest_enabled()) {
+        if (!notified && !qtest_driver()) {
             fprintf(stderr,
                     "main-loop: WARNING: I/O thread spun for %d iterations\n",
                     MAX_MAIN_LOOP_SPIN);

stubs/qtest.c

@@ -12,3 +12,8 @@
 
 /* Needed for qtest_allowed() */
 bool qtest_allowed;
+
+bool qtest_driver(void)
+{
+    return false;
+}