Refactor: libcrmcommon: pcmk__deleted_xml_t:path is now gchar

Avoids strdup() in free_xml_with_position(). g_string_free(xpath, FALSE)
frees the GString while transferring ownership of the underlying gchar
string to deleted_obj->path.

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