Remove dependencies on maruel/ut package client.
Remove dependencies on maruel/ut package client.

This is the last of several commits to remove the depedency on the
maruel/ut package and instead use smartystreets/goconvey.

This commit removes all remaining depedencies in luci-go/client/.
This was code used in the main package, rather than in unit tests.

R=maruel@chromium.org, nodir@chromium.org, vadimsh@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2678813004

luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go,luci/luci-go