Packed structures like struct uuid are not aligned. GCC 9.1 therefore
throws an error when trying to compile gen_rand_uuid().

lib/uuid.c: In function ‘gen_rand_uuid’:
lib/uuid.c:244:2: error: converting a packed ‘struct uuid’ pointer
(alignment 1) to a ‘unsigned int’ pointer (alignment 4) may result in
an unaligned pointer value [-Werror=address-of-packed-member]
  244 |  unsigned int *ptr = (unsigned int *)&uuid;
      |  ^~~~~~~~

Generate the uuid in a properly aligned buffer.

The byte order of a random number should not matter. Do not call
cpu_to_be32() to change the byte order.
Reported-by: NRamon Fried <rfried.dev@gmail.com>
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>