fdo#77890: page break exported as section break if different 1st page is set

- Page break was getting exported as section break in case if the different
  first page was set.
- Fixed this issue and added a UT.
- For additional details regarding the issue please check the following
   https://www.libreoffice.org/bugzilla/show_bug.cgi?id=77890#c2

Reviewed on:
	https://gerrit.libreoffice.org/9234

Change-Id: I6799b204c0d1c80a7e07119e2e3aac337520cb08