Failure recover for client side

[HarrisChu]

1. start client and then connect a graph address.
2. query forever
3. shutdown the graph service
4. wait for 3 seconds
5. start the graph service

expected result:
after graph restart, the client query successfully

actual result:
always raise error

1. if the connection is invalid, it would turn back the pool, and would exceed the max connection limit
   

2. if the err is write: broken pipe, it would always be an error here