Currently the api is inconsistent: requiring a uuid for the
host_id of the node to be removed, while the ignored nodes list
is given as comma-separated ip addresses.
Instead, support identifying the ignored_nodes either
by their host_id (uuid) or ip address.
Also, require all ignore_nodes to be of the same kind:
either UUIDs or ip addresses, as a mix of the 2 is likely
indicating a user error.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>