Feed guids broken again. (BB-7898)

You broke the <guid> of commits in the feed at https://bitbucket.org/<user>/rss/feed , so that commits won't show up in some feed readers, for example Thunderbird. Issues with feed guids has appeared and been fixed numerous times. I first noticed it when comments in commits didn't show up in the feed. That was fixed, but later the same thing happened to created issues. Now that is fixed, but now the commits are not shown in the feed. All commits have <guid isPermaLink="true">https://bitbucket.org/<user>/<repo>/commits/all</guid> which means that a feed reader would see all the entries as one, and ignore all but the first entry. Please remember that the <guid> of each feed entry must be unique (that is the "u" in "guid"), even if the link is to the same page.