Wrong num_tests in verdi computer test when fails to open a connection

[khsrali]

If verdi computer test fails in connection stage, it shows something like:

Report: Testing computer<sshFabric_baby> for user<[email protected]>...
* Opening connection... [FAILED]: Error while trying to connect to the computer
  Use the `--print-traceback` option to see the full traceback.
Warning: 1 out of 0 tests failed

reports the total run tests as zero. The reason is here the context manager fails on __enter__ before adding up 1 to num_tests

try:
    echo.echo('* Opening connection... ', nl=False)

    with transport:
        num_tests += 1

I think this is because, it was assumed that connection can never fail once core.ssh is set up. However this may not be the case always #6154