shell tests should report their results

Looking at the kea 1.5.0 postmortem see bullet 6.1 in line 56 (also action in line 66), we discovered that shell tests were failing, but the make check target was passing.

We need to improve our shell tests framework to report results in a similar way as gtest (generate xml with test names and their results).

Also, can make the tests look better by using start and end messages more similar to what gtest produces.