Fix occassional test_sfp_insert_events failure (sonic-net#215)

Due to rare timing issue test_sfp_insert_events failure can fail. Out of 100 iterations, the test failed on 82nd iteration.

Signed-off-by: Prince George <prgeor@microsoft.com>

sonic-xcvrd/tests/test_xcvrd.py

@@ -407,11 +407,12 @@ def test_sfp_insert_events(self):
         start = time.time()
         while True:
             _wrapper_soak_sfp_insert_event(sfp_insert_events, insert)
-            assert not bool(insert)
             if time.time() - start > MGMT_INIT_TIME_DELAY_SECS:
                 break
+            assert not bool(insert)
         assert insert == port_dict
 
+
     def test_sfp_remove_events(self):
         from xcvrd.xcvrd import _wrapper_soak_sfp_insert_event
         sfp_insert_events = {}
@@ -423,4 +424,4 @@ def test_sfp_remove_events(self):
             time.sleep(1)
             _wrapper_soak_sfp_insert_event(sfp_insert_events, removal)
 
-        assert port_dict == removal
+        assert port_dict == removal