Apply golangci-linter suggestions

Prepare btpeer_manager to be moved in infra. Fix linter problems

Change-Id: Id31ebe4ade9316ba3e62e6dd39b4547046775706
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/6244287
Reviewed-by: Jason Stanko <jstanko@google.com>
Commit-Queue: Alexandr Astrouski <astrouski@google.com>
Tested-by: Alexandr Astrouski <astrouski@google.com>
7 files changed