fix(overlay): take 1 on stable event (#3013)

Author: Tibing

src/framework/theme/components/cdk/overlay/dynamic/dynamic-overlay.spec.ts

@@ -332,7 +332,7 @@ describe('dynamic-overlay', () => {
     expect(instance.context).toBe(newContext);
     expect(instance.content).toBe(newContent);
     expect(renderContentSpy).toHaveBeenCalledTimes(3);
-    expect(updatePositionSpy).toHaveBeenCalledTimes(4);
+    expect(updatePositionSpy).toHaveBeenCalledTimes(3);
   });
 
   it('should set component', () => {

src/framework/theme/components/cdk/overlay/dynamic/dynamic-overlay.ts

@@ -1,5 +1,5 @@
 import { ComponentFactoryResolver, ComponentRef, Injectable, NgZone, Type } from '@angular/core';
-import { filter, takeUntil, distinctUntilChanged } from 'rxjs/operators';
+import { filter, takeUntil, distinctUntilChanged, take } from 'rxjs/operators';
 import { Subject, BehaviorSubject, Observable, merge } from 'rxjs';
 
 import { NbAdjustableConnectedPositionStrategy, NbPosition } from '../overlay-position';
@@ -234,7 +234,7 @@ export class NbDynamicOverlay {
       filter((destroyedOverlay: NbOverlayRef) => destroyedOverlay === overlay),
     );
 
-    this.zone.onStable.pipe(takeUntil(merge(this.destroy$, overlayDestroy$))).subscribe(() => this.updatePosition());
+    this.zone.onStable.pipe(take(1), takeUntil(merge(this.destroy$, overlayDestroy$))).subscribe(() => this.updatePosition());
   }
 
   protected updatePosition() {