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

Change-Id: I9e61f9f8fbdcf10985c52828b2bfbec64b4234f0
Reviewed-on: https://chromium-review.googlesource.com/1171957
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>