mds: encode truncate_pending in inode
mds: encode truncate_pending in inode

Otherwise we don't actually journal this value, and we get confused when
we replay a start_truncate and try to restart it.

Fixes: #1756
Signed-off-by: Sage Weil <c5b6ff1fd4f0bde10db63d7a3e07166cf6c4229f@dreamhost.com>

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