test: add command to 'Boot fail' message

When a timeout occurs while executing a command a 'Boot fail' message is
written and testing is stopped. The user is left in the dark about the
failure cause.

    ! _pytest.outcomes.Exit: Boot fail: Marking connection bad - no other tests will run !

Add the executed command to the message.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
1 file changed