sysvinit: use known hostname $host instead of (incorrectly) recalculating

We would need to do hostname -s on the remote node, not the local one.
But we already have $host; use it!

Reported-by: Xiaoxi Chen <xiaoxi.chen@intel.com>
Signed-off-by: Sage Weil <sage@inktank.com>
sysvinit: fix osd weight calculation on remote hosts

We need to do df on the remote host, not locally.

Simlarly, the ceph command uses the osd key, which exists remotely; run it there.

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