Add bundle command mapping check to make it compatible with rvm1-capistrano3 and other gems that use sshkit command mapping

[redvulps]

[ydkn]

Thanks for the PR.

Two remarks/question: Any particular reason why you aren't using SSHKit.config.command_map[:bundle] directly instead of accessing only the prefix SSHKit.config.command_map.prefix[:bundle] and then adding the bundle command itself again (+ ' bundle')? If prefix[:bundle] isn't a array or it has multiple prefixes using bundle_mapped.first will fail or won't include the the entire command - at least I think that would happen.

[redvulps]

Hmmm, that's a behavior of capistano3-rvm1, I'll check rbenv to see if it behaves different and update the code. Thanks for the advice!

[ydkn]

I made the changes I was talking about in branch command_map. It would be great if you could try if this still works in your env.