crush: fix "crush create-or-move/move" would drop osd's class

crush: fix "crush create-or-move/move" would drop osd's class

    Was:
     ./bin/ceph osd tree
    ID CLASS WEIGHT  TYPE NAME                                        UP/DOWN REWEIGHT PRI-AFF
    -1       3.00000 root default
    -2       3.00000     host gitbuilder-ceph-rpm-centos7-amd64-basic
     0   ssd 1.00000         osd.0                                         up  1.00000 1.00000
     1   ssd 1.00000         osd.1                                         up  1.00000 1.00000
     2   ssd 1.00000         osd.2                                         up  1.00000 1.00000

    ./bin/ceph osd crush move osd.0 root=foo rack=foo-rack  host=foo-host
    moved item id 0 name 'osd.0' to location {host=foo-host,rack=foo-rack,root=foo} in crush map

     ./bin/ceph osd tree
    ID CLASS WEIGHT  TYPE NAME                                        UP/DOWN REWEIGHT PRI-AFF
    -7       1.00000 root foo
    -6       1.00000     rack foo-rack
    -5       1.00000         host foo-host
     0       1.00000             osd.0                                     up  1.00000 1.00000
    -1       2.00000 root default
    -2       2.00000     host gitbuilder-ceph-rpm-centos7-amd64-basic
     1   ssd 1.00000         osd.1                                         up  1.00000 1.00000
     2   ssd 1.00000         osd.2                                         up  1.00000 1.00000

    Now:
    ./bin/ceph osd tree
    ID CLASS WEIGHT  TYPE NAME                                        UP/DOWN REWEIGHT PRI-AFF
    -1       3.00000 root default
    -2       3.00000     host gitbuilder-ceph-rpm-centos7-amd64-basic
     0   ssd 1.00000         osd.0                                         up  1.00000 1.00000
     1   ssd 1.00000         osd.1                                         up  1.00000 1.00000
     2   ssd 1.00000         osd.2                                         up  1.00000 1.00000

    ./bin/ceph osd crush move osd.0 root=foo rack=foo-rack  host=foo-host
    moved item id 0 name 'osd.0' to location {host=foo-host,rack=foo-rack,root=foo} in crush map

    ./bin/ceph osd tree
    ID CLASS WEIGHT  TYPE NAME                                        UP/DOWN REWEIGHT PRI-AFF
    -7       1.00000 root foo
    -6       1.00000     rack foo-rack
    -5       1.00000         host foo-host
     0   ssd 1.00000             osd.0                                     up  1.00000 1.00000
    -1       2.00000 root default
    -2       2.00000     host gitbuilder-ceph-rpm-centos7-amd64-basic
     1   ssd 1.00000         osd.1                                         up  1.00000 1.00000
     2   ssd 1.00000         osd.2                                         up  1.00000 1.00000

Signed-off-by: xie xingguo <xie.xingguo@zte.com.cn>