Bug#14323614 Assert !dict_index_is_online_ddl(index)
 || dict_index_is_clust(index) || (flags & BTR_CREATE_FLAG)

Race conditions are possible in online secondary index creation
(WL#5526) when a successfully created index is removed by
rollback_inplace_alter_table(), usually due to a lock wait timeout
while waiting for the meta-data lock needed for
commit_inplace_alter_table(commit=true).

The non-DDL code (insert, update/delete, purge, rollback) was not
prepared for the fact that index->online_status could be changed from
ONLINE_INDEX_COMPLETE to ONLINE_INDEX_ABORTED or
ONLINE_INDEX_ABORTED_DROPPED by rollback_inplace_alter_table().

Transaction rollback was accidentally race-free, because row_undo()
holds dict_operation_lock S-latch, which conflicts with the X-latch
acquired by rollback_inplace_alter_table(). But we fix the code anyway
to avoid a regression if we later get rid of the S-latch in rollback.

dict_index_online_trylog(): Replace with row_log_online_op_try().
Always check index->online_status while holding index->lock.

dict_stats_should_ignore_index(): Fix a potential race condition
between rollback_inplace_alter_table() and statistics collection. Do
not try to collect statistics for any secondary indexes that are being
or were created online, but have not been published yet.

row_ins_sec_mtr_start_and_check_if_aborted(): Add the parameter search_mode
to see if index->lock should be acquired in S or X mode.

row_ins_sec_index_entry_low(): Invoke row_log_online_op() if needed.
This replaces the dict_index_online_trylog() call in
row_ins_sec_index_entry().

row_log_online_op(): Allow the caller to hold index->lock in S or X mode.

row_purge_remove_sec_if_poss_tree(),
row_purge_remove_sec_if_poss_leaf(): Check index->online_status after
acquiring index->lock. These replace the check in
row_purge_remove_sec_if_poss().

row_undo_ins_remove_sec_low(): Check index->online_status after
acquiring index->lock. This replaces the check in
row_undo_ins_remove_sec_rec().

row_undo_mod_del_mark_or_remove_sec_low(): Check index->online_status
after acquiring index->lock. This replaces the check in
row_undo_mod_del_mark_or_remove_sec().

row_undo_mod_del_unmark_sec_and_undo_update(): Check
index->online_status after acquiring index->lock.

row_upd_sec_index_entry(): Check index->online_status after acquiring
index->lock, and log the change if needed. This fixes the reported
assertion failure.

row_upd_sec_online(): Remove.

row_upd_sec_step(): Remove the checks for online index creation. They
are now part of row_upd_sec_index_entry().

rb:1412 approved by Jimmy Yang