Fix screenshot surface null during animation

The screenshot surface might be set as null during animation if
previous animation still running and end during current animation
finished.

Fix this by only keep one animatior and cancel previous one before
new one start.

Fix: 263550337
Test: manual
Test: pass existing test
Change-Id: I95eb1b03790d84bdab7e58c25a7b0a1d074adfb8