coreMQTT misjudgment of transmission success leading to unsent data

[VanNamDinh]

1. coreMQTT may assume that the transmission was successful even though the FIT module (r_cellular, r_ether_rx) failed due to an error when sending MQTT messages by coreMQTT.

2. This causes unsent data.

[VanNamDinh]

Cellular case ,the following issue has also been fixed in v1.1.1 at ff20642