Don't allocate four times more space than needed. Duh.

* subversion/tests/libsvn_subr/adler32-test.c
  (make_random_data): We just worked out how many 32-bit random
   integers we'll generate, so maybe allocate space for only so many?


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1931369 13f79535-47bb-0310-9956-ffa450edef68