iotests: Replace time.clock() with Timeout

time.clock() is deprecated since Python 3.3. Current Python versions
warn that the function will be removed in Python 3.8, and those warnings
make the test case 118 fail.

Replace it with the Timeout mechanism that is compatible with both
Python 2 and 3, and makes the code even a little nicer.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>

tests/qemu-iotests/118

@@ -53,21 +53,17 @@ class ChangeBaseClass(iotests.QMPTestCase):
         if not self.has_real_tray:
             return
 
-        timeout = time.clock() + 3
-        while not self.has_opened and time.clock() < timeout:
-            self.process_events()
-        if not self.has_opened:
-            self.fail('Timeout while waiting for the tray to open')
+        with iotests.Timeout(3, 'Timeout while waiting for the tray to open'):
+            while not self.has_opened:
+                self.process_events()
 
     def wait_for_close(self):
         if not self.has_real_tray:
             return
 
-        timeout = time.clock() + 3
-        while not self.has_closed and time.clock() < timeout:
-            self.process_events()
-        if not self.has_opened:
-            self.fail('Timeout while waiting for the tray to close')
+        with iotests.Timeout(3, 'Timeout while waiting for the tray to close'):
+            while not self.has_closed:
+                self.process_events()
 
 class GeneralChangeTestsBaseClass(ChangeBaseClass):