add last callback run stamp to device records

src/include/switch_core.h

@@ -103,6 +103,7 @@ typedef struct switch_device_record_s {
 	switch_device_state_t last_state;
 	switch_time_t active_start;
 	switch_time_t active_stop;
+	switch_time_t last_call_time;
 	struct device_uuid_node_s *uuid_list;
 	struct device_uuid_node_s *uuid_tail;
 	switch_mutex_t *mutex;

src/switch_channel.c

@@ -4795,6 +4795,8 @@ static void switch_channel_check_device_state(switch_channel_t *channel, switch_
 		}
 	}
 
+	drec->last_call_time = switch_micro_time_now();
+
 	drec->last_state = drec->state;
 
 	switch_mutex_unlock(drec->mutex);