When /system/bin/crash_dump is executed from the su domain, do not
perform a domain transition. This allows processes run from that domain
to crash normally without SELinux interfering.

Bug: 114136122
Test: cferris: "This change works for me. I ran the crasher executable on
  /data, /data/nativetest, /data/nativetest64 (and even /data/local/tmp).
  All of them show that crash_dump can read the executables."
Change-Id: Ic135d61b11774acff37ebfb35831497cddbefdef