Problem was that 4k page size is not really supported in
Galera. For reference see:
	codership/galera#398

Page size 4k is problematic because WSREP XID info location
that was set to constant UNIV_PAGE_SIZE - 3500 and that is conflicting
with rseg undo slots location if there is lot of undo tablespaces.
Undo tablespace identifiers and page numbers require
at least 126*8=1024 bytes starting from offset 56. Therefore,
WSREP XID startig from offset 596 would overwrite several
space_id,page_no pairs starting from 72th undo log tablespace
space_id,page_no pair at offset 594.
This will cause InnoDB startup failure seen as
[ERROR] InnoDB: Unable to open undo tablespace './undo30579'.

Originally, the undo tablespace ID would always be between
0 and 127. Starting with MySQL 5.6.36 which introduced
Bug #25551311 BACKPORT BUG #23517560 REMOVE SPACE_ID RESTRICTION
FOR UNDO TABLESPACES (merged to MariaDB 10.0.31)
it is possible for an undo tablespace ID to be 0x7773. But in
this case, the page number should be 3, not 0x72650003.
This is just the first collision. The WSREP XID data would
overwrite subsequent slots.

trx0sys.h

trx0sys.cc
	Code formatting and add comments.