uMQTT_Simple: Return ping result instead of None

[magnus-0]

Suggestion for a small change in line 205 ('section' #PINGRESP in function wait_msg):

return res[0]

instead of:

return None

This allows you to check in your own consumer code that called check_msg() or wait_msg(), that the ping response came by and was valid:

if(oReply == 0xD0): # valid ping response

Thanks!