liblog: gate write on log id available

- Secure LOG_ID_KERNEL in writer
- Secure LOG_ID_SECURITY in reader and writer
- if writer transport says not available, do not write to that log id

Bug: 27566046
Bug: 27896341
Change-Id: If63a78a56fb94adfbf9979454c4cadb81af45c19
4 files changed
tree: 4bb3f48b26fae5b3f95f0ad9d4add3349ed4213a
  1. liblog/
  2. logcat/
  3. logd/
  4. logwrapper/