Fix davautocheck.sh for VPATH builds with a single test (i.e. 'davautocheck.sh basic').
Fix davautocheck.sh for VPATH builds with a single test (i.e. 'davautocheck.sh
basic').

* subversion/tests/cmdline/davautocheck.sh
  (main): Refer to the test directory explicitly instead of assuming that
  ABS_BUILDDIR is equal to the SCRIPTDIR.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion