fix addurl behavior when location and url logs are inconsistent

The url log could have an url for a key, while the location log thinks it's
not present in the web. In this case, addurl --file url would not do
anything. Fixed it to re-add the web as a location.

I don't know how this situation could arise, but I saw it in the wild in
the conference_proceedings repo, affecting key
URL-s17806003--http://mirror.linux.org.au/pub/linux.conf.au/2014/Wednesday/53-Building_Effective_Alliances_around_the_Trans-Pacific_Partnershi-c0505b631127ccc67e38e637344d988e
Investigating the presence log, it looked like that key
was originally listed as present in the web, then in commit
56abf9e9f3e691ed9d83513037d4019313321ca3 someone else's git-annex
set it and some other things to not present in the web. It would be
interesting to know what that user did, but I doubt I'll be able to find
out. All I can tell from this investigation is that the inconsistency was
not introduced when originally addurl-ing the url.

Command/AddUrl.hs

@@ -210,7 +210,7 @@ addUrlChecked relaxed url u checkexistssize key
 	| relaxed = do
 		setUrlPresent u key url
 		next $ return True
-	| otherwise = ifM (elem url <$> getUrls key)
+	| otherwise = ifM ((elem url <$> getUrls key) <&&> (elem u <$> loggedLocations key))
 		( next $ return True -- nothing to do
 		, do
 			(exists, samesize) <- checkexistssize key

Logs/Web.hs

@@ -54,9 +54,9 @@ getUrlsWithPrefix key prefix = filter (prefix `isPrefixOf`) <$> getUrls key
 setUrlPresent :: UUID -> Key -> URLString -> Annex ()
 setUrlPresent uuid key url = do
 	us <- getUrls key
-	unless (url `elem` us) $ do
+	unless (url `elem` us) $
 		addLog (urlLogFile key) =<< logNow InfoPresent url
-		logChange key uuid InfoPresent
+	logChange key uuid InfoPresent
 
 setUrlMissing :: UUID -> Key -> URLString -> Annex ()
 setUrlMissing uuid key url = do