tests: sev: Test launch-security with specific QEMU version

tests: sev: Test launch-security with specific QEMU version

In order to test SEV we need real QEMU capabilities. Ideally, this would
be tested with -latest capabilities, however, our capabilities are
currently tied to Intel HW, even the 2.12.0 containing SEV were edited by
hand, so we can only use that one for now, as splitting the capabilities
according to the vendor is a refactor for another day. The need for real
capabilities comes from the extended SEV platform data (PDH, cbitpos,
etc.) we'll need to cache/parse.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>