Revert "Strip exec* permissions from unconfined domains."

As discussed in https://android-review.googlesource.com/78634 , the removal of execmem may cause OTA problems. Not sure...

Revert this patch to give us more time to investigate.

This reverts commit 4e416ea4.

Change-Id: Ie05f90235da5b9ee20b374298494cbc0a58b9b49