filejournal: make io contiguous in write_bl() for directio
filejournal: make io contiguous in write_bl() for directio

Previously we were splitting the io for writing the header plus first
segment following a wrap.

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph