net: lib: coap: fix path and query options init

Fix options initialization for path and query
when a final segment is one character long.

For example, "a/b" inits path as ["a"] instead
of expected ["a", "b"]. The same applies to
query option. The "a/abc?a&b"  options won't
contain "b".

Signed-off-by: Georgij Cernysiov <geo.cgv@gmail.com>

subsys/net/lib/coap/coap_client.c

@@ -198,7 +198,7 @@ static int coap_client_init_path_options(struct coap_packet *pckt, const char *p
 		}
 	}
 
-	if (path_start < path_end) {
+	if (path_start < path_length) {
 		if (contains_query) {
 			ret = coap_packet_append_option(pckt, COAP_OPTION_URI_QUERY,
 							path + path_start,