tests/opr/jhash-t.c: Fix unsigned constant warning

tests/opr/jhash-t.c: Fix unsigned constant warning

Resolves this warning on 32-bit GCC:

jhash-t.c: In function ‘main’:
jhash-t.c:60:4: warning: this decimal constant is unsigned only in ISO C90
    is_int(3704403432, opr_jhash(test, 2, 0),
    ^
jhash-t.c:62:4: warning: this decimal constant is unsigned only in ISO C90
    is_int(3704403432, opr_jhash_int2(test[0], test[1], 0),
    ^

Change-Id: Ie3ab0f5aacdc719fa63f32e545b5863ec351f5eb
Reviewed-on: http://gerrit.openafs.org/11961
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>