backout gflag for setting mlock rlimit
backout gflag for setting mlock rlimit

Summary:
It is not used, it is not namespaced, and this is best set by the supervisor anyway.

Backout of: D24063687 (https://github.com/facebook/folly/commit/d6ed060efe7f9ea291fc78362d7f83c1c197f219).

Differential Revision: D32787797

fbshipit-source-id: 7231741e3f0b7b098fbfc65acb363ed560b20937

facebook/folly,facebook/folly,facebook/folly,facebook/folly,facebook/folly