vmspawn: try to set up swtpm state for 4K RSA keys support

vmspawn: try to set up swtpm state for 4K RSA keys support

The next version of swtpm will support RSA4096, but it needs to be called
with a new parameter in order to do so. Try with it first, and if
execution fails, fallback to running without it.

This is especially needed for OBS builds, as the signing key is RSA4096
and cannot be changed by users, so the generated UKIs have RSA4096 signatures
for the pcrsig sections, and swtpm refuses them without the new support.