Navigation: Remove initialDst and correctly handle location update for a sequence

Remove references to ```initialDst``` from the code. Make sure the URL is correct for the sequence start -> internal page when the initial URL is of the form protocol://path/to/page.html#/path/to/other-page.html (i.e., the resulting URL must be protocol://path/to/other-page.html#internal-page-id, not protocol://path/to/page.html#internal-page-id).

Fixes gh-7177