fix(inputs.mqtt): Reference correct password variable

[nexeck]

For me, connecting to MQTT with username/password and mqttv5 stopped working.
Not sure, but shouldn't it be cfg.Password instead of the config.Password Type?

[telegraf-tiger]

Thanks so much for the pull request!
🤝 ✒️ Just a reminder that the CLA has not yet been signed, and we'll need it before merging. Please sign the CLA when you get a chance, then post a comment here saying !signed-cla

[nexeck]

!signed-cla

[telegraf-tiger]

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[nexeck]

Telegraf 1.25.3 works for me with mqtt output, mqtt v5 and EMQX as an MQTT Server.
Beginning with telegraf 1.26.0 EMQX isn't accepting any connection from telegraf anymore.
reason: {shutdown,bad_username_or_password}

[powersj]

This in fact does look like a regression, but from a commit last week, long after v1.26.0.

TIL that there is a Password variable in the config module lol

[srebhan]

O M G! Thanks for catching this @nexeck!