Pull mft comparison into proc_parser_mft_pre()

Pull mft comparison into proc_parser_mft_pre()

This way we can be sure more easily that both manifests are non-NULL,
thus avoiding some NULL checks and risk of use-after-free. This also
makes it clearer which manifest is the "older" one and will simplify
an upcoming commit doing issuance time comparison.

This adds a bit of a hack to proc_parser_mft_pre() to ensure we don't
look into DIR_TEMP in noop mode.

ok job