mds: fix uninitialized LeaseStat for null lease
mds: fix uninitialized LeaseStat for null lease

./include/encoding.h: In member function void
Locker::issue_client_lease(CDentry*, client_t, ceph::bufferlist&, utime_t,
Session*):
 ./include/encoding.h:80: warning: e.LeaseStat::duration_ms may be used
uninitialized in this function

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