support/scripts/pkg-stats: check_url_status(): use HEAD requests to limit server load

The gnu.org admins have been blocking the IP address of machines running
pkg-stats as the GET requests for the (many) packages with gnu.org URLs are
seen as abusive.

The resource body is not used, so use a HTTP HEAD request instead of a GET
to limit server load and bandwidth use.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Julien Olivain <ju.o@free.fr>
(cherry picked from commit f9f3e6ccc6)
Signed-off-by: Thomas Perale <thomas.perale@mind.be>

support/scripts/pkg-stats

@@ -469,7 +469,7 @@ async def check_url_status(session, pkg, npkgs, retry=True, verbose=False):
     global check_url_count
 
     try:
-        async with session.get(pkg.url) as resp:
+        async with session.head(pkg.url) as resp:
             if resp.status >= 400:
                 pkg.status['url'] = ("error", "invalid {}".format(resp.status))
                 check_url_count += 1