fix:fix consul heartbeat delay.

Author: SkyeBeFreeman

polaris-plugins/polaris-plugins-connector/connector-consul/src/main/java/com/tencent/polaris/plugins/connector/consul/ConsulAPIConnector.java

@@ -312,6 +312,8 @@ public CommonProviderResponse registerInstance(CommonProviderRequest req, Map<St
                 resp.setExists(false);
                 LOG.info("Registered service to Consul: " + service);
                 ieRegistered = true;
+                // heartbeat when registration is successful.
+                heartbeat(req);
                 return resp;
             } catch (ConsulException e) {
                 throw new RetriableException(ErrorCode.NETWORK_ERROR,