[AUDIT] do not panic on exclude messages in audit_log_pid_context()

If we fail to get an ab in audit_log_pid_context this may be due to an exclude
rule rather than a memory allocation failure.  If it was due to a memory
allocation failue we would have already paniced and no need to do it again.
Signed-off-by: NEric Paris <eparis@redhat.com>

kernel/auditsc.c

@@ -948,7 +948,7 @@ static int audit_log_pid_context(struct audit_context *context, pid_t pid,
 
 	ab = audit_log_start(context, GFP_KERNEL, AUDIT_OBJ_PID);
 	if (!ab)
-		return 1;
+		return rc;
 
 	audit_log_format(ab, "opid=%d oauid=%d ouid=%d oses=%d", pid, auid,
 			 uid, sessionid);