api: ceph ec pools: move to format-str, create ec in worker, reuse $rados

api: ceph ec pools: move to format-str, create ec in worker, reuse $rados

moved to a format string 'erasurce-coded', that allows also to drop
most of the param existence checking as we can set the correct
optional'ness in there.  Also avoids bloating the API to much for
just this.

Reuse the $rados connection more often to avoid to much
overhead/lingering sockets (the rados connection stays around in the
background to allow efficient reuse)

really should be three separate commits, but too intertwined and too
late for me to care tbh.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>