Merge pull request #7621 from IgniteUI/bug-fix-slider-9.1.x

fix(slider): emit onchange callback correctly
fix(slider): remove commented code

Author: rkaraivanov

projects/igniteui-angular/src/lib/slider/slider.component.ts

@@ -625,8 +625,6 @@ export class IgxSliderComponent implements
         } else {
             this._value = value;
         }
-
-        this._onChangeCallback(value);
     }
 
     /**
@@ -1420,10 +1418,12 @@ export class IgxSliderComponent implements
     public setValue(value: number | IRangeSliderValue) {
         if (!this.isRange) {
             this.upperValue = value as number - (value as number % this.step);
+            this._onChangeCallback(this.upperValue);
         } else {
             value = this.validateInitialValue(value as IRangeSliderValue);
             this.upperValue = (value as IRangeSliderValue).upper;
             this.lowerValue = (value as IRangeSliderValue).lower;
+            this._onChangeCallback({lower: this.lowerValue, upper: this.upperValue});
         }
     }