fix(modal): clean up animation when disabled
fix(modal): clean up animation when disabled

- When the animation is set to false, do not remove the `in` class to prevent black opaque background from showing

Closes #4740
Fixes #4672

byronigoe/bootstrap,Lincoln-xzc/angular-ui-bootstrap,burlhock/bootstrap,icfantv/bootstrap,Kpler/bootstrap,looker/bootstrap,Foxandxss/bootstrap,wesleycho/bootstrap,benhalverson/bootstrap,Servoy/bootstrap,byronigoe/bootstrap,wesleycho/bootstrap,angular-ui/bootstrap,christor/bootstrap,RobJacobs/bootstrap,vfiles/bootstrap,looker/bootstrap,icfantv/bootstrap,caoruiy/bootstrap,mabi/bootstrap,Kpler/bootstrap,pdsoftplan/bootstrap,benhalverson/bootstrap,292388900/bootstrap,matteopic/bootstrap,shiftagent/ui-bootstrap,angular-ui/bootstrap,christor/bootstrap,vfiles/bootstrap,caoruiy/bootstrap,Servoy/bootstrap,shootermv/bootstrap,fpipita/bootstrap,fpipita/bootstrap,shiftagent/ui-bootstrap,pdsoftplan/bootstrap,justin-john/bootstrap-1,matteopic/bootstrap,mabi/bootstrap,deeg/bootstrap,Lincoln-xzc/angular-ui-bootstrap,292388900/bootstrap,RobJacobs/bootstrap,connyay/bootstrap,Foxandxss/bootstrap,deeg/bootstrap,davious/angular-ui-bootstrap,BookingBug/bootstrap,benhalverson/bootstrap,davious/angular-ui-bootstrap,infowrap/bootstrap,justin-john/bootstrap-1,BookingBug/bootstrap,benhalverson/bootstrap,shootermv/bootstrap,connyay/bootstrap,infowrap/bootstrap,burlhock/bootstrap