Bug with empty list for DnsSearch

[DimitriiIgnatev]

I try update DnsSearch=[] by docker-py, and find that problem for set up parameter dns_search=[]

[GordonTheTurtle]

Please sign your commits following these rules: https://github.com/moby/moby/blob/master/CONTRIBUTING.md#sign-your-work The easiest way to do this is to amend the last commit:

$ git clone -b "dns_search" [email protected]:DimitriiIgnatev/docker-py.git somewhere
$ cd somewhere
$ git commit --amend -s --no-edit
$ git push -f

Amending updates the existing PR. You DO NOT need to open a new one.