Fix performance regression with anchor brush in sculpt mode

When restoring coordinates in sculpt mode (used for several brushes
including anchor brush), can use sculpt_undo_get_node() for
non-dyntopo sculpting instead of sculpt_undo_push_node().

This should bring speed of anchor brush back to 2.65 level for regular
mesh/multires sculpting.

Fixes projects.blender.org/tracker/?func=detail&atid=498&aid=34208&group_id=9

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54601 954f8c5b-7b00-dc11-b283-0030488c597c