Renames MobileContext::getMobileHost() to getMobileHostToken()

This method returns to the mobile-specific token from a mobile domain or
mobile domain template, so the rename aims to better clarify what this
method actually does. I updated the docblock to also help make it more
clear.

Also, added some test cases for this method.

Change-Id: Ibcc8b5082cdda8223f69c748c0713abaf8385fd1
Merge "Renames MobileContext::getMobileHost() to getMobileHostToken()"