Pass node for br callback too

Not passing the node here prevented the original separator source from being
used in some cases, which caused rt failures in pages like 'en:Ayat al-Kursi'.
This page now round-trips without failures. There are no changes in
parserTests, which suggests that this area is in need of additional tests.

Change-Id: I618cb2801e1433f46596691af932122f54db91bb