pull: Add http2=false remote config option

This seems to work around
https://github.com/ostreedev/ostree/issues/1362

Though I'm not entirely sure why yet. But at least with this it'll be easier for
people to work around things locally.

Closes: #1368
Approved by: jlebon

src/libostree/ostree-fetcher.h

@@ -50,7 +50,8 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC(OstreeFetcher, g_object_unref)
 typedef enum {
   OSTREE_FETCHER_FLAGS_NONE = 0,
   OSTREE_FETCHER_FLAGS_TLS_PERMISSIVE = (1 << 0),
-  OSTREE_FETCHER_FLAGS_TRANSFER_GZIP = (1 << 1)
+  OSTREE_FETCHER_FLAGS_TRANSFER_GZIP = (1 << 1),
+  OSTREE_FETCHER_FLAGS_DISABLE_HTTP2 = (1 << 2),
 } OstreeFetcherConfigFlags;
 
 typedef enum {