Update rfc.sh to add change-id to commit message.

If the commit hook is installed, ammend the commit message
so change-id gets added to it.

Change-Id: I3d256a6fa73e789b02bad86421dd95e0a1f52a78
Reviewed-on: https://review.openstack.org/284
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Tested-by: Jenkins

tools/rfc.sh

@@ -35,6 +35,8 @@ set_hooks_commit_msg()
     curl -o $f $u || wget -O $f $u;
 
     chmod +x $f;
+
+    GIT_EDITOR=/bin/true git commit --amend
 }
 
 add_remote()