raft: Forbid server address 0 as it has special meaning
raft: Forbid server address 0 as it has special meaning

Server address UUID 0 is not a valid server id since there is code that
assumes if server_id is 0 the value is not set (e.g _voted_for).

Prevent users from manually setting this invalid value.

Signed-off-by: Alejo Sanchez <004be06a28e38b437b038f9b5c0b9f5758b792e9@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla