Make the target arguments to sbox.simple_rm() etc. be relpaths relative to

Make the target arguments to sbox.simple_rm() etc. be relpaths relative to
sbox.wc_dir, instead of OS-style paths relative to CWD. This is part of a
continuing bid to simplify the repetitive bulky parts of regression tests.

* subversion/tests/cmdline/svntest/sandbox.py
  (Sandbox.ospath): Add a doc string.
  (Sandbox.ospaths): New function.
  (simple_update, simple_commit, simple_rm, simple_mkdir, simple_add,
   simple_revert, simple_propset, simple_propdel): Use ospaths() to adjust
    the target arguments.

* subversion/tests/cmdline/basic_tests.py,
  subversion/tests/cmdline/copy_tests.py,
  subversion/tests/cmdline/diff_tests.py,
  subversion/tests/cmdline/lock_tests.py,
  subversion/tests/cmdline/merge_tests.py,
  subversion/tests/cmdline/prop_tests.py,
  subversion/tests/cmdline/schedule_tests.py
    Adjust calls.

git-svn-id: http://svn.apache.org/repos/asf/subversion/trunk/subversion/tests/cmdline@1031610 13f79535-47bb-0310-9956-ffa450edef68