liblog: deal with warning messages

(cherry pick from commit b525884edb1f8a80a8fc6cad58c69bdacc5bdb90)

- Fix bug in fake_log_devices when it can not allocate memory
  failing to use the full on-stack buffer as backup.
- remove superfluous code.

Bug: 27265662
Change-Id: I97b6cca5f4ce8ecad9beb3a08353de596d6a4ad1
2 files changed