fix(donut): avoid regenerating chart on every data update
fix(donut): avoid regenerating chart on every data update

This smooths out the animation when transitioning between data sets

dlabrecq/patternfly-ng,patternfly/patternfly-ng,dlabrecq/patternfly-ng,patternfly/patternfly-ng,patternfly/patternfly-ng,dlabrecq/patternfly-ng,patternfly/patternfly-ng,dlabrecq/patternfly-ng