core: AsyncTaskDAO proper newline logging

Used the %n platform independent newline instead of the platform
specific \n in AsyncTaskDAODbFacadeImpl's logging.

This addresses the VA_FORMAT_STRING_USES_NEWLINE FindBugs warning.

Change-Id: I1bf28f3006b24f121d1c97ac1034f03e62c51d6e
Signed-off-by: Allon Mureinik <amureini@redhat.com>