virttest.standalone_test: Fix t_type undefined error

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
virttest.bootstrap: Fix #1426 - subtests.cfg generation for dropin tests

Turns out we were passing the incorrect information to
the snippets of dropin tests, causing

./run -t qemu --run-dropin

To fail. Dropin tests come from io-github-autotest-qemu,
so let's hardcode that information.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #1429 from autotest/fix-1426

Fix 1426