Preserve the "end of list" flag for xls round-tripping.

This "end of list" flag determines whether the row insertion was an
automatic insertion at the bottom.  Calc doesn't use this at the moment
but Excel uses it to differentiate a normal row insertion from an
automatic one.

Change-Id: I6b28669d816c54d1dc1e4c106918ba688415788d
(cherry picked from commit adf0d7b1fb8eed88f4fcd6d31662ae6f59d00812)
Reviewed-on: https://gerrit.libreoffice.org/10311
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>