bcli: Filter for full nodes on getpeerinfo

[nepet]

@NicolasDorier pointed out that fetching blocks from peers is slowed down due to us not filtering for nodes with a the serviceflag NODE_NETWORK set.

lightning/plugins/bcli.c

Lines 630 to 633 in 9c39410

	JSON_SCAN(json_to_int, &id)) == NULL) {
	// fixme: future optimization: a) filter for full nodes,
	// b) sort by last ping
	tal_arr_expand(&stash->peers, id);