Refactor: libcrmcommon: Consider pre-/post-upgrade XSLT failures fatal

This way, if any XSL transform in the enter -> base -> leave pipeline
fails, the entire pipeline is considered failed. This changes behavior,
but if the enter or leave transform fails then we likely have bigger
problems.

This will make planned changes possible.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>