crash_dump: dontaudit CAP_SYS_PTRACE denial.

Bug: http://b/34853272
Test: debuggerd -b `pidof zygote`
Change-Id: I0b18117754e77cfa94cf0b95aff32edb578b1a95

public/crash_dump.te

@@ -8,6 +8,11 @@ allow crash_dump {
   -keystore
   -logd
 }:process { ptrace signal sigchld sigstop sigkill };
+
+# crash_dump might inherit CAP_SYS_PTRACE from a privileged process,
+# which will result in an audit log even when it's allowed to trace.
+dontaudit crash_dump self:capability { sys_ptrace };
+
 userdebug_or_eng(`
   allow crash_dump logd:process { ptrace signal sigchld sigstop sigkill };
 ')