runtime: disable protection check

enableProtection() is called when confidential_guest=true, so we
disable this check to allow us to test running with
confidential_guest=true and sev_snp_guest=false.

Note this was already done by Wedson previously to allow testing on
non-SNP CPUs, but the purpose here is different.

src/runtime/virtcontainers/clh.go

@@ -474,7 +474,8 @@ func (clh *cloudHypervisor) enableProtection() error {
 		return nil
 
 	default:
-		return errors.New("This system doesn't support Confidential Computing (Guest Protection)")
+		// Allow running with no hardware protection for testing.
+		return nil
 	}
 }