I've not been able to get the mqtt `connfail` callback to work.
I'm consistently receiving `method not supported` errors:
```
application.lua:53: method not supported
stack traceback:
[C]: in function 'on'
application.lua:53: in main chunk
[C]: in function 'dofile'
init.lua:18: in function <init.lua:6>
```
Example code:
```
function on_connection_failed(client, reason)
print("mqtt connection failed: " .. reason)
end
m:on("connfail", on_connection_failed)
```
I believed this to be caused by the incorrect length comparison for `connfail`
that is updated here.
Once I changed that, the error went away, however the callback was never called.
I believe the callback was never called because of an incorrect assignment.
However, I saw this somewhat confusing description in the docs so this
assignment may be expected?
> The second (failure) callback aliases with the "connfail" callback available through :on(). (The "offline" callback is only called after an already established connection becomes closed. If the connect() call fails to establish a connection, the callback passed to :connect() is called and nothing else.)
e547c2a094