Clear remove button coordinates when not enabled.

Previously, the remove button coordinates were only updated upon
positioning. This led to the possibility coordinates for a previously
visible button would be considered when removing became enabled. This
changelist fixes the issue by clearing it when removing is disabled and
likewise only updating when enabled.

Test: manual
Fixes: 341072351
Flag: EXEMPT bugfix
Change-Id: I53d2536e487ad0937400d771e61ffb04ecadef7e