fix(carousel): fix navigation control display
fix(carousel): fix navigation control display

Closes #238

chenyuzhcy/ng-bootstrap,deeg/ng-bootstrap,ACGC/ng-bootstrap,ng-bootstrap/core,ng-bootstrap/ng-bootstrap,ng-bootstrap/ng-bootstrap,chenyuzhcy/ng-bootstrap,deeg/ng-bootstrap,maxokorokov/core,Foxandxss/ngbs-demo,Foxandxss/ng-bootstrap,mschoudry/ng-bootstrap,spongessuck/ng-bootstrap,jnizet/ng-bootstrap,jnizet/ng-bootstrap,jnizet/ng-bootstrap,ktriek/ng-bootstrap,pkozlowski-opensource/core,Foxandxss/ngbs-demo,spongessuck/ng-bootstrap,ng-bootstrap/core,ng-bootstrap/core,maxokorokov/core,CrustyJew/ng-bootstrap,pkozlowski-opensource/core,benouat/ng-bootstrap,spongessuck/ng-bootstrap,CrustyJew/ng-bootstrap,deeg/ng-bootstrap,mschoudry/ng-bootstrap,johnbenz13/ng-bootstrap,jnizet/ng-bootstrap,fbasso/ng-bootstrap,ng-bootstrap/ng-bootstrap,johnbenz13/ng-bootstrap,benouat/ng-bootstrap,maxokorokov/core,ACGC/ng-bootstrap,fbasso/ng-bootstrap,Xaiid/ng-bootstrap,chenyuzhcy/ng-bootstrap,ng-bootstrap/ng-bootstrap,maxokorokov/core,CrustyJew/ng-bootstrap,spongessuck/ng-bootstrap,Xaiid/ng-bootstrap,benouat/ng-bootstrap,ktriek/ng-bootstrap,Xaiid/ng-bootstrap,mschoudry/ng-bootstrap,Foxandxss/ngbs-demo,Foxandxss/ng-bootstrap,Foxandxss/ng-bootstrap,pkozlowski-opensource/core,CrustyJew/ng-bootstrap,fbasso/ng-bootstrap,johnbenz13/ng-bootstrap,fbasso/ng-bootstrap,ACGC/ng-bootstrap,ktriek/ng-bootstrap,ktriek/ng-bootstrap,deeg/ng-bootstrap,benouat/ng-bootstrap