3.0 - Consistent usage of short echo and sprintf

Refs https://github.com/cakephp/cakephp/pull/4079.

Went with sprintf() since it does fall a little closer in line with CS (even though, yeah, the CS is about echo, and printf() is different) and the benchmarking difference between the two is minuscule.
Nice catch. In error500 too. Got it.