sd-bus: allow localhost addresses

By settings AI_ADDRCONFIG in hints we cannot for example resolve "localhost"
when the local machine only has a loopback interface. This seems like an
unnecessary restriction, drop it.

Inspired by https://bugzilla.redhat.com/show_bug.cgi?id=1839007.

TODO

@@ -561,6 +561,9 @@ Features:
 * sd-bus: add vtable flag, that may be used to request client creds implicitly
   and asynchronously before dispatching the operation
 
+* sd-bus: parse addresses given in sd_bus_set_addresses immediately and not
+  only when used. Add unit tests.
+
 * make use of ethtool veth peer info in machined, for automatically finding out
   host-side interface pointing to the container.
 

src/libsystemd/sd-bus/sd-bus.c

@@ -782,7 +782,6 @@ static int parse_tcp_address(sd_bus *b, const char **p, char **guid) {
         int r;
         struct addrinfo *result, hints = {
                 .ai_socktype = SOCK_STREAM,
-                .ai_flags = AI_ADDRCONFIG,
         };
 
         assert(b);