Currently bup only indexes physical parent paths; adjust tests.

Fix tests that fail on systems where components of the parent path are
symlinks (like /tmp on OS X).  i.e. if you run:

  bup index /x/y/z

bup might actually store

  /a/z...

if y is a symlink to a.  See index-cmd.py and index.reduce_paths().

Signed-off-by: Zoran Zaric <zz@zoranzaric.de>
[rlb@defaultvalue.org: handle test.sh fix differently; add realpath();
 adjust commit message.]
Signed-off-by: Rob Browning <rlb@defaultvalue.org>