When wsrep is enabled, for any update on innodb tables, the
corresponding keys are appended to galera's transaction writeset
(wsrep_append_keys()). However, for LOAD DATA, this got skipped
if binary logging was disabled or it was non-ROW based.
As a result, while the updates from LOAD DATA on non-partitioned
tables replicated fine as wsrep implicitly enables binary logging
(if not enabled, explicitly), the same did not work on partitioned
tables as for partitioned tables the binary logging gets disabled
temporarily (ha_partition::write_row()).

Fixed by removing the unwanted conditions from the check.
Also backported some changes from 10.0-galera to make sure
wsrep_load_data_splitting affects LOAD DATA commands only.