spec: Use GitHub source URL

Primary download location for released source tarballs is for
quite some time GitHub so change spec file to use it.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>

corosync.spec.in

@@ -25,7 +25,7 @@ Version: @version@
 Release: 1%{?gitver}%{?dist}
 License: BSD-3-Clause
 URL: http://corosync.github.io/corosync/
-Source0: http://build.clusterlabs.org/corosync/releases/%{name}-%{version}%{?gittarver}.tar.gz
+Source0: https://github.com/%{name}/%{name}/releases/download/v%{version}/%{name}-%{version}%{?gittarver}.tar.gz
 
 # Runtime bits
 # The automatic dependency overridden in favor of explicit version lock