fix Carousel style bug

https://github.com/iview/iview/issues/6076

src/components/carousel/carousel.vue

@@ -113,10 +113,13 @@
                 ];
             },
             trackStyles () {
+                // #6076
+                const visibleStyle = this.trackIndex === -1 ? 'hidden' : 'visible';
                 return {
                     width: `${this.trackWidth}px`,
                     transform: `translate3d(${-this.trackOffset}px, 0px, 0px)`,
-                    transition: `transform 500ms ${this.easing}`
+                    transition: `transform 500ms ${this.easing}`,
+                    visibility : visibleStyle
                 };
             },
             copyTrackStyles () {
@@ -125,7 +128,7 @@
                     transform: `translate3d(${-this.trackCopyOffset}px, 0px, 0px)`,
                     transition: `transform 500ms ${this.easing}`,
                     position: 'absolute',
-                    top: 0
+                    // top: 0
                 };
             },
             arrowClasses () {

src/styles/components/carousel.less

@@ -24,7 +24,8 @@
 
     &-track {
         position: relative;
-        top: 0;
+        //top: 0;
+        top: 100%;
         left: 0;
         display: block;
 
@@ -33,6 +34,7 @@
         z-index: 1;
         &.higher {
             z-index: 2;
+            top: 0;
         }
     }