Icons Pack: Register a svg - HTML attr status does't work

Hi ! :)

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

- [x] bug report
- [ ] feature request

**Issue description**
**Current behavior:**

I imported a custom SVG icon using [this code from documentation](https://github.com/akveo/nebular/issues/2089#issue-526683696).

Then used a nb-icon with a `status="primary"`. As follows :
``
Icons takes SVG file base color.

**Expected behavior:**
Icon takes color from HTML status (primary, danger ...)