[tesh] Fix arguments in tesh file

[tesh] Fix arguments in tesh file

Example:

    $ tesh with_mutex_handling.tesh --cfg=model-check/reduction:none
    Test suite from stdin

- remove the options from the tesh @ARGV before handling the .tesh
  file;

- GetOptions() can't modify the locally-scoped (my) @ARGV, use the
  global one instead.