This patch will force wait for MQTT ACK (connection) and also
fix the issue caused by "strlen(mqtt_cfg.msg) + 1" that will
include the "\0" in the payload. It's forbidded by MQTT spec.
Some MQTT servers will ignore it, others like TagoIO will refuse
the packet.
commit 36d4bfa774 set a hostname to work
around getaddrinfo failing. getaddrinfo returns a non-zero value on
error, and there should be an early return after the error message is
printed.
