Disable DIRECT_IO for LUKS header with unaligned keyslots.

Fixes issue#287.

Such a header is very rare, it is not worth to do more detection here.

lib/utils_device.c

@@ -530,3 +530,8 @@ size_t size_round_up(size_t size, unsigned int block)
 	size_t s = (size + (block - 1)) / block;
 	return s * block;
 }
+
+void device_disable_direct_io(struct device *device)
+{
+	device->o_direct = 0;
+}