Refactor: libcrmcommon: Clean up xml_create_patchset()

Check valid format sooner. Improve variable names and scopes. Drop trace
messages that aren't particularly helpful. (They may also be inaccurate:
if the config didn't change, the top-level <cib> element may have
changed; this does not imply the status section changed.)

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