Add disconnect causes for WFC use cases.

Add new disconnect cause used when an attempt is made to place an
emergency call over WFC but the service is unavailable.
Add new disconnect cause when WFC is not available in an area.

Bug: 128993720
Test: Unit tests added to confirm remapping.
Change-Id: I15dcff8fabc06b5d469d083b0970fe0e77e7d318