Pull default instead of tip during updates

I've just realized that during updates we're pulling tip instead of default.

For example, this is the current situation on release channel for French (and other locales)
http://hg.mozilla.org/releases/l10n/mozilla-release/fr/graph

tip: GECKO1708esr_2013080515_RELBRANCH (Firefox 17 ESR)
default: FIREFOX_23_0_BUILD1 (Firefox 23)

So, searching for "browser/chrome/browser/browser.dtd:toolsMenu.label" will show the string from tip ("Outils") instead of the only really used on Firefox 23 ("Outils de développement").