improve file-copy performance in docker using rsync

[s1061123]

At that time, toad with docker uses 'copy:' module instead of 'synchronize:' module because docker connection in ansible does not support rsync that 'synchronize:' module uses. But performance point of view, rsync is better performance as following document:
http://docs.ansible.com/ansible/copy_module.html#notes

Currently ansible-devel supprort rsync with docker at following PR.
ansible/ansible#18145

After merging (i.e. official release), we should catch up with the changes.

[leifmadsen]

@s1061123 I believe this is now available in the 2.2.1.0 release, so can you take a stab at working on this issue?

[s1061123]

I also checked tag "v2.2.2.0-0.2.rc2" and it does not have this fix yet...
https://github.com/ansible/ansible/blob/v2.2.2.0-0.2.rc2/lib/ansible/plugins/action/synchronize.py

So we may need to move it future release...

[leifmadsen]

Ah ok, for some reason I thought I saw the commit in 2.2.1.0 since it looked like it was merged in December 2016?

[leifmadsen]

I guess we'll be waiting for 2.3.0 for this change, so we'll just defer to a future milestone.