[log_listener] fix logic bug with 0-sized MaxCapacityFiles

A recent change to support MaxCapacityFiles with a max capacity of 0
bytes wasn't implemented correctly, and on writes claimed no bytes were
written to the always-empty file. Now, it will claim all bytes were
successfully written, as all bytes will always be correctly handled
(i.e. discarded) in this case.

TEST: added unit test to cover this case
Change-Id: I734422257430bb7e527ea47068ebaa36fb285892
1 file changed