Make sure we have physical path back from mktemp

Darwin actually symlinks /var inside /private, but mktemp reports back
the logical pathat time of file creation.  So make sure we always get
the full physical path to be absolutely certain when doing comparisons
later, because thats how the Ruby status_shortcuts.rb script is going to
obtain them.
declare original location of cmds

The previous tests assumed default locations for all commands, however
they do not exist in the same place on all *nixes.  I encountered this
when the test was failing on MacOSX where it was expected hardcoded
`/bin/sed` when in fact the code was identifying the correct local
expansion of `/usr/bin/sed`.

To make this test more robust, it now checks for the original location
of all cmds and uses that in its expansion tests for
`test_shell_command_wrapping()`.
scripts should exit rather than return

some shells are pickier about this.  darwin uses a newer version of sh
that complains about it.  this is the ‘proper’ behavior in either
scenario.