librados: rados_X_command need to assemble a vector from char *cmd

The old monitors take a vector with words split; new monitors don't
care, but the old ones do

Signed-off-by: Dan Mick <dan.mick@inktank.com>
ceph: translate -s to status for old mons as well

Signed-off-by: Dan Mick <dan.mick@inktank.com>
rados.py: make exception with errno string instead of int

Signed-off-by: Dan Mick <dan.mick@inktank.com>
ceph: improve error reporting on failure to connect to cluster

Signed-off-by: Dan Mick <dan.mick@inktank.com>