Add a retry timeout for failed dns lookups

[TysonAndre]

DNS lookups block the main thread for several milliseconds. This can cause issues if dns is misconfigured or a host is decommissioned, especially if there is no dns caching

[2021-05-03 10:56:34.205] nc_server.c:954 key 'key' on dist 0 maps to server 'invalid123141:6379:1'
[2021-05-03 10:56:34.430] nc_util.c:556 address resolution of node 'invalid123141' service '6379' failed: Name or service not known

static void
server_resolve(struct server *server, struct conn *conn)
{