pull: move bookmark movements inside the `exchange.pull` There is no reason for bookmarks to get a special treatment. As a first step we move the code as is in the `exchange.pull` function. Integration with the rest of the flow will come later. Adding bookmarks to pull means that most clone paths are now pulling bookmarks through pull. We ensure that bookmark-update messages are properly suppressed in that case. In test-pull-http.t the 'requesting all changes' message disappear because we now get the authentication error on the `listkeys`command before such message is printed.