Stopping Spinners in ngOnInit

**I'm submitting a ...** (check one with "x")

- [ ] bug report
- [x] feature request

### Issue description

**Current behavior:**
if you put the change of the variable linked to the spinner showing in the ngOnInit, it does not stop the spinner. It does not matter if you wait for http.get or if you just use setTimeout like in the examples.

if you use a button click event to change the variable, it works

**Expected behavior:**
Spinners should be stopped in ngOnInit, too, as this is the place where you load data from APIs

**Related code:**
```
https://github.com/AtzederSerbe/Nebular-Test

import { Component } from '@angular/core';

@Component({
selector: 'app-home',
templateUrl: './home.component.html',
})
export class HomeComponent {
loading = true;
NgOnInit() {
setTimeout(() => this.loading=false,3000) // doesnt work
}

//works
setOff() {
this.loading = false;
}
setOn() {
this.loading = true;
}

```

html:
```

Home Component Card Test

On
Off
```

### Other information:

**npm, node, OS, Browser**
```
npm v 6.9.0
```

**Angular, Nebular**
```
"dependencies": {
"@angular/animations": "8.0.0",
"@angular/common": "8.0.0",
"@angular/compiler": "8.0.0",
"@angular/core": "8.0.0",
"@angular/forms": "8.0.0",
"@angular/platform-browser": "8.0.0",
"@angular/platform-browser-dynamic": "8.0.0",
"@angular/platform-server": "8.0.0",
"@angular/router": "8.0.0",
"@nguniversal/module-map-ngfactory-loader": "8.0.0-rc.1",
"core-js": "^2.6.5",
"rxjs": "^6.5.2",
"zone.js": "0.9.1",
"aspnet-prerendering": "^3.0.1",
"bootstrap": "^4.3.1",
"jquery": "3.3.1",
"oidc-client": "^1.6.1",
"popper.js": "^1.14.3",
"@nebular/theme": "4.1.0",
"@angular/cdk": "8.0.0",
"@nebular/eva-icons": "4.1.0",
"ng-http-cache": "1.2.0",
"eva-icons": "1.1.1"
},
"devDependencies": {
"@angular-devkit/build-angular": "0.801.0-beta.2",
"@angular/cli": "8.0.0",
"@angular/compiler-cli": "8.0.0",
"@angular/language-service": "8.0.0",
"@types/jasmine": "~3.3.12",
"@types/jasminewd2": "~2.0.6",
"@types/node": "~11.10.5",
"codelyzer": "~4.5.0",
"jasmine-core": "~3.3.0",
"jasmine-spec-reporter": "~4.2.1",
"karma": "^4.0.0",
"karma-chrome-launcher": "~2.2.0",
"karma-coverage-istanbul-reporter": "~2.0.5",
"karma-jasmine": "~2.0.1",
"karma-jasmine-html-reporter": "^1.4.2",
"typescript": "3.4.5"
},
"optionalDependencies": {
"node-sass": "4.12.0",
"protractor": "~5.4.0",
"ts-node": "~5.0.1",
"tslint": "~5.9.1"
}
```