Allow USER@FQDN format for bootstrap (and chef_client?) commands about knife-zero

[sawanoboly]

--ssh-user was just inherited(copy) from chef-core.

If limited to the case of bootstraping, using user@hostname format could be nice. I think it also supported by the chef-core.

And I think Chef-Server users(like me) are familiar with QUERY than knife-solo usage.

[patcon]

From the cli docs, I wasn't aware chef-core supported this, but perhaps it would be best-suited there, so knife-zero would get it for free :)

[patcon]

Created a core issue here as well: chef/chef#3527

[patcon]

OK, submitted a PR upstream. Thanks! Feel free to +1 the feature if you think it's valuable

[sawanoboly]

includes chef v12.6.0

https://github.com/chef/chef/blob/master/CHANGELOG.md#1260

[sawanoboly]

Released as v1.11.0, Thanks 👍

[patcon]

:)