Only trim /services from the end of crowd.server.url

Crowd's configuration for a REST client will throw away /services, on the assumption that it's been given a SOAP URL.

However, the current filter doesn't confirm that the removed string is at the end of the URL, so:

http://example.com/services/crowd

would become: http://example.com, rather than being left unaffected.

Make the check more specific, so that it only matches at the end of the string.
Filter should still truncate legacy URLs of SecurityServer, so that http://example.com/services/SecurityServer should become http://example.com.

To summarise, the filter should truncate following possible URL suffixes: /services[/SecurityServer][/], leaving all other unchanged.

As a workaround, add a redundant '/services' at the end of the URL, which will be removed, but which will leave the rest of the path unaffected:

http://example.com/services/crowd/services