Revert "Reset stack guard after fork from Zygote"

A performance regression was noticed in go/lem benchmarks for ART.  This
was likely caused by an issue in the related CL in the ART project.

Reason for revert: performance regression
Reverted Changes:
Ie0c81f97f:Remove stack protector from some interpreter funct...
Iaf565a374:Reset stack guard after fork from Zygote

Bug: 168258494
Change-Id: I1a415829b7714ad99014fbc67786c5608c81104c