Ensure crash_dump cannot be allowed to ptrace itself.

This is not needed and could conceivably be abused.

Test: Builds.
Bug: 110107376
Change-Id: I73f301439af435fe40b3902409964cdf6e2c7dd5

private/crash_dump.te

@@ -24,3 +24,5 @@ neverallow crash_dump {
   vendor_init
   vold
 }:process { ptrace signal sigstop sigkill };
+
+neverallow crash_dump self:process ptrace;