libcephfs: get osd location on -1 should return EINVAL

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit b88af07ef5a3c9a484255b54149a6e6a635845dc)

c70331db13bdbf1f967ece48cdbec28b97c3d19c backported some
CRUSH changes which necessitate backporting this as well, or
we get failures like successfully looking up an OSD with ID -1.
Reviewed-by: Greg Farnum <greg@inktank.com>