Refactor: libcrmcommon: Drop getDocPtr() from internal code

Other than a few exceptions where a doc isn't needed, we create all new
XML nodes via create_xml_node(). This ensures that the newly created
node has a doc. Therefore, we don't need a getter function that creates
and assigns a doc not present.

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