mgr/cephadm/schedule: make placement shuffle deterministic

mgr/cephadm/schedule: make placement shuffle deterministic

hash(str) is non-deterministic, probably because it is using the internal
object ID or something and not the string content?

In any case, explicitly hash the string content and use that instead.

Also, sort the input pre-shuffle to ensure that variations in the original
host list ordering don't screw with the result.

Signed-off-by: Sage Weil <sage@newdream.net>