crush: fix force to behave with non-root TAKE
crush: fix force to behave with non-root TAKE

If the (first) TAKE in the crush rule is not the root, see if they picked
a point somewhere beneath the appropriate part of the hierachy.  If not,
continue with a normal mapping.

Previously we would simply error out in this case and map nothing.

Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

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