Disable "ostree trivial-httpd" by default now

This goes farther along the path of deprecating it; consumers should
have been ported at this point.  Though probably a lot of people
may still use `rpm-ostree-toolbox`.

Closes: #723
Approved by: jlebon

src/ostree/main.c

@@ -58,7 +58,7 @@ static OstreeCommand commands[] = {
   { "show", ostree_builtin_show },
   { "static-delta", ostree_builtin_static_delta },
   { "summary", ostree_builtin_summary },
-#ifdef HAVE_LIBSOUP 
+#if defined(HAVE_LIBSOUP) && defined(BUILDOPT_ENABLE_TRIVIAL_HTTPD_CMDLINE)
   { "trivial-httpd", ostree_builtin_trivial_httpd },
 #endif
   { NULL }