tools/ocaml: Drop int_array_of_uuid_string()

tools/ocaml: Drop int_array_of_uuid_string()

This function is entirely internal to xenctrl stubs, and serves only to
convert the uuid string to an integer array (making 16 memory allocations as
it goes), while the C stubs turns the integer array back into a binary array.

Instead, pass the string all the way down into C, and have sscanf() unpack it
directly into a xen_domain_handle_t object.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>