staging: lustre: obdclass: simplify class_uuid_unparse

This patch simplifies uuid unparse logic by using sprintf "%pU" extension.
And eliminates the code with a coding style error:

ERROR: Macros with complex values should be enclosed in parentheses
+#define CONSUME(val, ptr) (val) = consume(sizeof(val), (ptr))

Signed-off-by: Vasiliy Korchagin <vasiliy.korchagin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>