loadtest: enable comparisons with different configs

Description

Currently we provide a convenient way to compare two MM builds through the `ltctl comparison` command.
This however can only test changes in code but otherwise runs both installations with the same config.
The goal of this ticket is to enable comparisons of two instances running different configs.

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Mana

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Unassigned

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Reporter

Claudio Costa

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Mattermost Team

Server

Sprint

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