audit: don't needlessly reset valid wait time

After auditd has recovered from an overflowed queue, the first process
that doesn't use reserves to make it through the queue checks should
reset the audit backlog wait time to the configured value.  After that,
there is no need to keep resetting it.
Signed-off-by: NRichard Guy Briggs <rgb@redhat.com>
Signed-off-by: NPaul Moore <pmoore@redhat.com>

kernel/audit.c

@@ -1400,7 +1400,7 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 		return NULL;
 	}
 
-	if (!reserve)
+	if (!reserve && !audit_backlog_wait_time)
 		audit_backlog_wait_time = audit_backlog_wait_time_master;
 
 	ab = audit_buffer_alloc(ctx, gfp_mask, type);