fix: fixed #185 delta speed evaluation

Author: cuprumtan

github-actions-tests/sources/agent_3.4.0.conf

@@ -41,7 +41,10 @@ def send(self, key, value, delta=None, host=None, clock=None, only_positive_spee
                     last_value, last_time = self._last_values[hash_key]
                     self._last_values[hash_key] = (value, clock)
                     if delta == Plugin.DELTA.speed_per_second:
-                        value = float(value - last_value) / (clock - last_time)
+                        if last_time == clock:
+                            pass
+                        else:
+                            value = float(value - last_value) / (clock - last_time)
                     if delta == Plugin.DELTA.simple_change:
                         value = float(value - last_value)
                 else: