recheck the logic of ocitools --host-specific generate

[haiyanmeng]

The logic of ocitools --host-specific generate should be rechecked and behave as it is supposed to be.
Here are two examples:

1. if the user runs ocitools --host-specific generate --linux-cpu-shares=512 on a windows machine, the --linux-cpu-shares should be ignored.
2. if the user run ocitools --host-specific generate --output config.json on a windows machine, the config.json file should not include the linux section.

[haiyanmeng]

@wking , I remembered there is an issue relative to this one opened by you. Right?
If there already has one, let me know and I will close this one.

[wking]

On Fri, Aug 05, 2016 at 12:29:24PM -0700, hmeng-19 wrote:

@wking , I remembered there is an issue relative to this one opened
by you. Right? If there already has one, let me know and I will
close this one.

Also host-specific (but for validate) is #132. I made a host-specific
generate comment in 1, but this can be about things like that.

[haiyanmeng]

@wking , thanks for pointing out.
Then I will leave this issue open and work on a PR to fix the problem.