Revert "Update uthash to the latest version."

This reverts commit 36a86e50.

Turns out this needs more work than expected.  hash_part_inx is used
afterwards and HASH_FCN no longer uses/sets it.

For future reference it looks like in the new code you would just
call HASH_TO_BKT after calling HASH_FCN.  I didn't want to spend
time testing it, so just rolled back the code.  As this is the only
place in the entirity of Slurm we currently use it I am not super
concerned.

NOTE: the macro HASH_FCN (which is really HASH_JEN) is identical in
both places outside the already explained differences.