httppeer: do less splitting on httpheader value

We only care about the first value split off, so only split off the first
value.

mercurial/httppeer.py

@@ -112,7 +112,7 b' class httppeer(wireproto.wirepeer):'
         if len(args) > 0:
             httpheader = self.capable('httpheader')
             if httpheader:
-                headersize = int(httpheader.split(',')[0])
+                headersize = int(httpheader.split(',', 1)[0])
         if headersize > 0:
             # The headers can typically carry more data than the URL.
             encargs = urllib.urlencode(sorted(args.items()))