Simplify and refactor BytesSyncLogger
https://gitweb.torproject.org/user/dcf/snowflake.git/log/?h=refactor-byteslogger&id=73173cb6987dbf26fdb1036e4b7710c200f87141 https://gitweb.torproject.org/user/dcf/snowflake.git/diff/?h=refactor-byteslogger&id=73173cb6987dbf26fdb1036e4b7710c200f87141&id2=65ecb798ca8842a431214c2aa5133620e576c5f3
No longer needs a separate go logger.Log()
in the caller.