Closing the connection if client.Start returns an error.
Closing the connection if client.Start returns an error.

If during Start the connection is made, but an error is encountered later and start returns an error,
we should be closing the connection before returning to prevent leaking file descriptors.

Change-Id: Ibc68677768e4bf3d9694a588316affde2e36517b
Signed-off-by: Christie Deiters <e4468cc84aecfae6e99f0a34c860a09f92b5c65c@lutron.com>

wolfeidau/org.eclipse.paho.mqtt.golang,bcbroussard/mqtt-go,cwandrews/mqtt,yunba/mqtt.go,bcbroussard/mqtt-go,shoenig/go-mqtt,w3hacker/gomqtt,choonkeat/paho.mqtt.golang,bcbroussard/mqtt-go,yunba/mqtt.go,ivan4th/org.eclipse.paho.mqtt.golang,liqian1702/yunba_test,cwandrews/mqtt,ivan4th/org.eclipse.paho.mqtt.golang,w3hacker/gomqtt,ivan4th/org.eclipse.paho.mqtt.golang,cwandrews/mqtt,yunba/mqtt.go,shoenig/go-mqtt,ninjasphere/org.eclipse.paho.mqtt.golang,choonkeat/paho.mqtt.golang,ninjasphere/org.eclipse.paho.mqtt.golang,liqian1702/yunba_test,choonkeat/paho.mqtt.golang,wolfeidau/org.eclipse.paho.mqtt.golang