Workaround problem where Ndb_local_connection can't access the
warnings produced when running a SQL query, instead detect
if this a binlog thread and print the warning also to log.
NOTE! This can be removed when BUG#27507543 has been implemented
and instead log these warnings in a more controlled/selective manner
in Ndb_local_connection.

Change-Id: I20b44eb9f6049b2a7c75c6785326e86649841178