Bug 839312 - Specify gonk low-memory-killer priorityClasses in the correct order and fix typo in b2g.js which was preventing us from giving the kernel one of the necessary priority classes. r=jlebar, a=lsblakk

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extra : transplant_source : %DC%11%DE%E7%FF%FB%0B%F9q%26%25%C5%AB%F6%BE%9A%19%DFc%A7