mds: CInode: catch exception by reference, not value

CID 1251353

Signed-off-by: Greg Farnum <gfarnum@redhat.com>
mds: remove dead code from inode_t::compare()

CID 1251354

Signed-off-by: Greg Farnum <gfarnum@redhat.com>
Merge pull request #2894 from ceph/wip-scrub-coverity

Wip scrub coverity