Add check binary owner on PreCreateCheck()

[zchee]

See also #75

[johanneswuerbach]

This won't support sudo docker-machine create -d xhyve right? I would like if both cases are handled and the driver checks before every command stop, restart touching xhyve whether the permissions are correct. WDYT?

[zchee]

@johanneswuerbach That's correct.
PreCreateCheck() is only called when creating command.
I think need check owner before all commands such as PreCommandCheck()(or PreOwnerCheck?).
I will more fix when merged this PR.

but, Do we require corrective action of sudo?
Currently, there are users who would put the sudo before docker-machine command, but docker-machine other drivers are not instructed put the sudo.
So, I think solve if I write a more detail usage.
When install by Homebrew, users do not know how to use and flags, they will see this repository.

Check of the owner is required.
and, If does not exists $HOME/.docker directory, boot2docker.iso file and $HOME/.docker/machine/cache directory will be create by root owner.

• https://github.com/docker/machine/blob/master/libmachine/mcnutils/b2d.go#L397

This problem is also required improve.

WDYT?

Sorry, I am sleepy, English is rough... 🙀

[zchee]

@johanneswuerbach But put as insurance might be good!

[zchee]

@johanneswuerbach I created other issue.
It will tentatively merge this PR.

[johanneswuerbach]

Thanks, 🙇

[zchee]

@johanneswuerbach Create pull-request!
#78

Handling own binary owner, and sudo before docker-machine command.
It's probably working.