Fix stuck when reconnect broker (apache#703)

Signed-off-by: xiaolongran <[email protected]>

Fixes apache#697

### Motivation

As apache#697 said, In Go SDK, when the reconnection logic is triggered under certain conditions, the reconnection will not succeed due to request timeout.

Comparing the implementation of the Java SDK, we can see that each time the reconnection logic is triggered, the original connection will be closed and a new connection will be created.

![image](https://user-images.githubusercontent.com/20965307/148906906-1cfc5c07-1836-4185-94ec-e43f5565a4a8.png)


So in this pr, we introduced a new `reconnectFlag` field in the `connection` struct to mark the reconnection state. When the broker actively informs the client to close the connection to trigger the reconnection logic, we will store it from the `connections` cache of the `connectionPool`. The old connection object is deleted, and a new connection is created to complete the reconnection

### Modifications

- Add `reconnectFlag` in `connection` struct

pulsar/internal/connection.go

@@ -809,6 +809,8 @@ func (c *connection) handleCloseConsumer(closeConsumer *pb.CommandCloseConsumer)
 	consumerID := closeConsumer.GetConsumerId()
 	c.log.Infof("Broker notification of Closed consumer: %d", consumerID)
 
+	c.changeState(connectionClosed)
+
 	if consumer, ok := c.consumerHandler(consumerID); ok {
 		consumer.ConnectionClosed()
 		c.DeleteConsumeHandler(consumerID)
@@ -821,6 +823,8 @@ func (c *connection) handleCloseProducer(closeProducer *pb.CommandCloseProducer)
 	c.log.Infof("Broker notification of Closed producer: %d", closeProducer.GetProducerId())
 	producerID := closeProducer.GetProducerId()
 
+	c.changeState(connectionClosed)
+
 	producer, ok := c.deletePendingProducers(producerID)
 	// did we find a producer?
 	if ok {

pulsar/internal/connection_pool.go

@@ -75,13 +75,13 @@ func (p *connectionPool) GetConnection(logicalAddr *url.URL, physicalAddr *url.U
 	p.Lock()
 	conn, ok := p.connections[key]
 	if ok {
-		p.log.Debugf("Found connection in pool key=%s logical_addr=%+v physical_addr=%+v",
+		p.log.Infof("Found connection in pool key=%s logical_addr=%+v physical_addr=%+v",
 			key, conn.logicalAddr, conn.physicalAddr)
 
 		// remove stale/failed connection
 		if conn.closed() {
 			delete(p.connections, key)
-			p.log.Debugf("Removed connection from pool key=%s logical_addr=%+v physical_addr=%+v",
+			p.log.Infof("Removed connection from pool key=%s logical_addr=%+v physical_addr=%+v",
 				key, conn.logicalAddr, conn.physicalAddr)
 			conn = nil // set to nil so we create a new one
 		}