selftests/harness: prettify SKIP message whitespace again

Commit 9847d24a ("selftests/harness: Refactor XFAIL into SKIP")
replaced XFAIL with SKIP in the output. Add one more space to make the
output aligned and pretty again.

Fixes: 9847d24a ("selftests/harness: Refactor XFAIL into SKIP")
Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>