Stop sanity check from resetting module_compressed_suffix.

[sjuxax]

When installing a kernel that uses MODULE_COMPRESS_XZ from a kernel that uses MODULE_COMPRESS_GZIP, DKMS almost works. It builds the modules, keeps them in /var/lib/dkms, and mistakenly believes that it has successfully copied them into the target kernel's tree (which makes attempts to diagnose with dkms status or to rebuild with dkms install confusing, to say the least). Long night on this one.

The problem is that right before the installation, check_version_sanity runs. It fails to pass the intended kernel version to set_module_suffix, causing it to analyze the tree for uname -r and forget the compression suffix for the kernel we're trying to use. Let's fix that.

This PR works for now, but may want to consider removing the default parameter from set_module_suffix entirely to make sure this type of thing can't slip under the rug again.