Revert "Improved performance of flush_cache and prime_cache when paramet...

...ers are passed to them."

This reverts commit 76ba73412f6de3abe775464bba6a8ec9434fdc98.

We'll use the memoist gem instead since it contains what we need:
https://github.com/matthewrudy/memoist/pull/2

See https://github.com/ManageIQ/manageiq/pull/985