Add policy for /system/bin/auditctl

/system/bin/auditctl is executed by init to set the kernel audit
throttling rate limit. Grant the rules necessary for this to happen.

Test: compiles and boots
Test: Perform an operation which generates lots of SELinux denials,
      and count how many occur before and after the time period.
Bug: 118815957

(cherry picked from commit 622ab8a2ba498679175750694c997c6e350848ae)

Change-Id: Ie5b4852fa217462557fce192c764305893968454
diff --git a/private/file_contexts b/private/file_contexts
index f4aefe3..a42041a 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -182,6 +182,7 @@
 /system/lib(64)?(/.*)?		u:object_r:system_lib_file:s0
 /system/bin/atrace	u:object_r:atrace_exec:s0
 /system/bin/ashmemd	u:object_r:ashmemd_exec:s0
+/system/bin/auditctl	u:object_r:auditctl_exec:s0
 /system/bin/bcc                 u:object_r:rs_exec:s0
 /system/bin/blank_screen	u:object_r:blank_screen_exec:s0
 /system/bin/charger		u:object_r:charger_exec:s0