Network traffic annotation added to policy/core/common/cloud.

Network traffic annotation is added to network request of
components/policy/core/common/cloud/device_management_service.cc
components/policy/core/common/cloud/external_policy_data_fetcher.cc
components/policy/core/common/cloud/user_info_fetcher.cc

BUG=656607

Review-Url: https://codereview.chromium.org/2800653002
Cr-Commit-Position: refs/heads/master@{#468999}
3 files changed