Revert "libaudit: limit to 5 selinux denials per sec"

The shamu instabilities continued even after throttling SELinux denials
to 5/second. 5 denials per second is too low when doing device bringup,
and there have been some complaints about lost SELinux denials. See,
for example, http://comments.gmane.org/gmane.comp.security.selinux/21941

Bring the limit back up to 20/second to prevent dropping too many
denials on the floor.

This reverts commit a15db51bbf.

(cherrypick of commit 9667a66019)

Change-Id: I05e85cce0a792d05aa557fcc614c0fc019c15014

logd/libaudit.c

@@ -177,7 +177,7 @@ int audit_setup(int fd, uint32_t pid)
      */
     status.pid = pid;
     status.mask = AUDIT_STATUS_PID | AUDIT_STATUS_RATE_LIMIT;
-    status.rate_limit = 5; // audit entries per second
+    status.rate_limit = 20; // audit entries per second
 
     /* Let the kernel know this pid will be registering for audit events */
     rc = audit_send(fd, AUDIT_SET, &status, sizeof(status));