Modify sickbeard module paths

On my home server I have the following configuration of services available from the same domain:

/ - reverse proxy to maraschino
/sickbeard - reverse proxy to sickbeard
/couchpotato - reverse proxy to couchpotato
/transmission - reverse proxy to transmission

Generally this works, but I noticed that Maraschino used "/sickbeard" as a path prefix, which meant that proxied API calls from Maraschino's UI -> Maraschino -> Sickbeard were being routed directly to sickbeard and failing. This change modifies the maraschino routes to use "/xhr/sickbeard" instead, which mirrors the couchpotato module behavior and reduces the chance of path conflicts.