LOCSERVICES-4219 Adding support for bbc.com cookies.

Created a new method getCookieDomain() which determine which domain the locserv cookie should be set for.

Changed setLocServCookie() to an instance method rather than a function within persistLocation. This isolates the tests. There were not any tests that explicitly tested the logic in this method. Further tests could be added here eg testing the string passed to setCookieString (for domain, expiry time etc).