liblog: Statistics truncated to 16384 bytes

- if network read/write broken up, reassemble the pieces.
- Use a 20ms poll to check if a new fragment has been
  sent by the other side.
- fixup logd-unit-tests to take a (simplified) fragment
  from the liblog changes.

Bug: 14164765
Change-Id: I98ff87888c119e1e8349717646d0f733e8971bc8