Inconsistent error message with vm in an unknown state

[roy9495]

Issue #3659 Earlier when vm was in unknown state it was providing different error messages between 'restart' and 'start' Earlier

$ multipass restart charm-dev
restart failed: instance "charm-dev" is not running

$ multipass start charm-dev
start failed: The following errors occurred:
Instance 'charm-dev' is already running, but in an unknown state

Now

$ multipass restart charm-dev
restart failed: Instance 'Charm-dev' is already running, but in an unknown state
Use `multipass stop charm-dev`

$ multipass start charm-dev
start failed: The following errors occurred:
Instance 'Charm-dev' is already running, but in an unknown state
Use `multipass stop charm-dev`

[ricab]

Hey @roy9495, we'd need you to apply these formatting changes and also sign the CLA.

[georgeliao]

@roy9495 Thanks for the contribution. It looks good to me, the Positional Formatting usage is also fine here.