apps/restconf: fix compiler warning 'addr' may be used uninitialized

Natvie build with GCC 11.3 generates the following warning.  The patch
is silly and the code path should never be reached, but it silences the
compiler.

restconf_main_native.c:572:9: warning: ‘addr’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

apps/restconf/restconf_main_native.c

@@ -564,6 +564,9 @@ restconf_accept_client(int   fd,
         addr = &(in6->sin6_addr);
         break;
     }
+    default:
+        errno = EAFNOSUPPORT;
+        goto done;
     }
     if ((rsock->rs_from_addr = calloc(INET6_ADDRSTRLEN, 1)) == NULL){
         clicon_err(OE_UNIX, errno, "calloc");