Firefox Nightly is bugged, force moz audio usage

Firefox nightly as of today (v. 24) has these issues:

1) Every time a polyfill callback is "late", it doesn't drop the
request for the late polyfill, rather, it adds it to the upcoming
requests, so we overbuffer to infinity.

2) Failure to disconnect the previous polyfill event chain, causing
re-initializations of the audio code to do 2x (3x, 4x, and to infinity)
polyfill. Assuming some failure to GC.