add heartbeat_use_scheduler variable to force the heartbeat to use the scheduler…

add heartbeat_use_scheduler variable to force the heartbeat to use the scheduler rather than the media stream and also make it auto-chage between modes when going in and out of the media path

src/switch_core_media.c

@@ -7742,6 +7742,13 @@ SWITCH_DECLARE(switch_status_t) switch_core_media_receive_message(switch_core_se
 		}
 		goto end;
 
+	case SWITCH_MESSAGE_INDICATE_MEDIA:
+		{
+			if (session->track_duration) {
+				switch_core_session_enable_heartbeat(session, session->track_duration);
+			}
+		}
+		break;
 	case SWITCH_MESSAGE_INDICATE_NOMEDIA:
 		{
 			const char *uuid;
@@ -7781,6 +7788,10 @@ SWITCH_DECLARE(switch_status_t) switch_core_media_receive_message(switch_core_se
 				switch_core_media_absorb_sdp(session);
 			}
 
+			if (session->track_duration) {
+				switch_core_session_enable_heartbeat(session, session->track_duration);
+			}
+
 		}
 		break;
 

src/switch_core_session.c

@@ -1541,6 +1541,7 @@ SWITCH_DECLARE(void) switch_core_session_enable_heartbeat(switch_core_session_t
 	session->track_duration = seconds;
 
 	if (switch_channel_test_flag(session->channel, CF_PROXY_MODE) || 
+		switch_true(switch_channel_get_variable_dup(session->channel, "heartbeat_use_scheduler", SWITCH_FALSE, -1)) ||
 		switch_true(switch_channel_get_variable_dup(session->channel, "bypass_media", SWITCH_FALSE, -1)) ||
 		switch_true(switch_channel_get_variable_dup(session->channel, "bypass_media_after_bridge", SWITCH_FALSE, -1))) {
 		switch_log_printf(SWITCH_CHANNEL_SESSION_LOG(session), SWITCH_LOG_WARNING, "%s using scheduler due to bypass_media mode\n",