Fix "empty reply from server" curl-syndrome with url retrieval (RhBug:598988)

- We were adding a trailing newline to urlhelper command line passed
  to execvp(), with the newline ending up in the URL passed to curl.
  Many servers dont seem to mind the extra newline, but some do. Oh well...

rpmio/url.c

@@ -110,7 +110,7 @@ int urlGetFile(const char * url, const char * dest)
 
     /* XXX TODO: sanity checks like target == dest... */
 
-    rasprintf(&cmd, "%s %s %s\n", urlhelper, target, url);
+    rasprintf(&cmd, "%s %s %s", urlhelper, target, url);
     urlhelper = _free(urlhelper);
 
     if ((pid = fork()) == 0) {