selftest: wic: test default output directory

selftest: wic: test default output directory

As tests now explicitly specify output directory we don't
need test_alternate_output_dir test case. However, we need
to test wic output to default output location.

Removed test_alternate_output_dir test case.
Added test_default_output_dir test case.

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>