Change ns_server-resident Golang tools to use Go version 1.8.1
Change ns_server-resident Golang tools to use Go version 1.8.1

1.7.x won't be supported, apparently, by the time spock ships.
Plus there are some issues with go programs on OSX Sierra.

Change-Id: Ie27a644f9c313673aa01e65457a1fa4b50433bef
Reviewed-on: http://review.couchbase.org/77518
Tested-by: Dave Finlay <7b10a9ed9f70e64c30b07607a671ae61c33f14c8@couchbase.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server