1. If there is already a wipe tower on current plate, leave it there regardless need_wipe_tower flag.
This is useful when we have toolchange custom gcodes.
2. Correct wipe tower pos to prevent it outside bed.
Jira: STUDIO-4426
Change-Id: Iedecc7c5fe7ced01533d0a302253841046a7fb42
(cherry picked from commit e8d728e46b12baaf9fb0e87e3d14197ae3616826)