Bump the CIPD client version to
b482bfa19d3fa79b4b40dd5ac7a34479052e3df1. This version inculdes support
for the "-log-level" flag.

Update CIPD bootstrap scripts and tool installation scripts to log at
warning level, so that standard operation doesn't produce any logs.

This version differs from the previous CL in that the "selfupdate"
command no longer uses "-log-level". This fixes an issue where the
current CIPD, which doesn't support "-log-level", is given the flag
prior to actually updating to a version that does.

BUG=chromium:748651
TEST=canary
  - Tested this CIPD version on canary waterfall successfully.

Change-Id: I69dfe522d890eb307214f18d0467ce921a766446
Reviewed-on: https://chromium-review.googlesource.com/589568
Commit-Queue: Daniel Jacques <dnj@chromium.org>
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>