Jhack is incompatible with juju 2 controllers

[PietroPasotti]

Jhack ships with a juju 3 client. As a result it can't use certain commands with juju 2 controllers: juju status will work, but juju status --format=json will not.

This is the reason for #30

[PietroPasotti]

Workaround for SOME issues (juju ssh compatibility) is to use jhack from sources (not the snapped version). Commands that rely on juju cli output may still break, as some of that output (format) is inconsistent between juju versions.