devserver: pass a cache_user to initialize gsutil.

This CL passes an argument cache_user in gsutil initialization. This
'cache_user' is used to create cache directory for gsutil.

TEST=emerge chromite to local moblab DUT, call devserver to provision
it. Ran cros flash ssh://.

Change-Id: Ia5789ce18ac4d87e74ccf4f0bb9db7ec535cdccf
Commit-Ready: Xixuan Wu <>
Tested-by: Xixuan Wu <>
Reviewed-by: Gwendal Grignou <>
(cherry picked from commit 178263c26da66538203e47a28a102097a7cf2929)
Reviewed-by: Jinsong Mu <>
Tested-by: Keith Haddow <>
3 files changed