Fix for [#34747] Rendering invisible tiles
* reset_session() was not taking render percentage into account in case persistent_data was enabled.
* also deprecate old "maximsize" DNA variable. 

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55547 954f8c5b-7b00-dc11-b283-0030488c597c