mds/Capability: no copying

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-dencoder: add 'copy' command to test operator=

Signed-off-by: Sage Weil <sage@inktank.com>
osd/HitSet: fix Param::operator=()

We don't have a virtual operator= defined for each Param::Impl (nor do we
want to bother); use encode/decode instead!

Signed-off-by: Sage Weil <sage@inktank.com>
osd/HitSet: fix dump() of fpp

Signed-off-by: Sage Weil <sage@inktank.com>
wip