p-calendar's navigation (left/right) is not in sync with selected date, if date is not in current year

[ChristianMetzner]

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Plunkr Case (Bug Reports)
https://stackblitz.com/edit/github-eewso5

Current behavior
When navigating forward/backward calendar is initially setting the wrong year when the selected date is not within the current year.

Expected behavior
When navigating forward/backward calendar is setting the previous/next month, relying on the current selected date (year).

Minimal reproduction of the problem with instructions
Set a date that is not within the current year. Then click on backward navigation. Calendar is now setting the previous month, but using the current year, instead of the year which is set by the selection. Same happens on forward navigation

• Angular version: 6.1.2

• PrimeNG version: 6.1.0