forcibly disable roaming support in the client

ssh client security bug fix from
http://www.openssh.com/txt/release-7.1p2

openssh client is installed in gce instances.
although it's private key is not that much sensitive
it's better to land this security patch than not.

reported initially as cve-2016-0777 and cve-2016-0778
(January 14th, 2016)

BUG: 26587626
Change-Id: I113d576a3522ded8cb0f4a2e117999b0c51d4364