Linux and OSX only for now. This also rolls CIPD client to a version that
supports pinned hashes (v2.2.5).

CIPD_CLIENT_VER and CIPD_CLIENT_SRV are no longer supported as env vars, since
it makes no sense when pinning hashes of the binaries at specific version on
the specific backend.

Also somewhat cleanup 'cipd' script to use "${VAR}", stderr and colored output
consistently.

R=iannucci@chromium.org, nodir@chromium.org
BUG=870166, 874586

Change-Id: Iac67fbb6b5d07dcd81d44536737b03b146f1ad14
Reviewed-on: https://chromium-review.googlesource.com/1176727Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>