Refactor: libcrmcommon: Best practices in xml_log_patchset()

Add doxygen block, use bool instead of gboolean, limit scope of
variables, remove redundant patchset NULL check, reorder add/del
comparisons, fix indentation.

An upcoming commit will split format v1 and v2 into helper functions.

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