discard the unnecessary path

Hi I checked the code

Line 772 in 473b02d

    
           aimagepath = athumbpath + addpath + '/' + os.path.basename(folder_path) + '/.actors/' + aimagefilename

and found that it's unnecessary to include the full 'addpath' here.
the reasons are

suppose that the media is located at /volume1/Media/Movie/ppp and the actors folder is /volume1/Media/Movie/ppp/.actors
I can start a web server instance whose root path is '/volume1/Media', so http://localhost/Movie/ppp/.actors/A.jpg is accessible.
However, if I configure the 'path to movie library or global actor folder' as 'http://localhost/', the code will add '/volume1/Media/Movie' as 'addpath', but 'http://localhost/volume1/Media/Movie/ppp/.actors/A.jpg' does exist.
So I suggest here besides the 'path to movie library or global actor folder', we add the 'root path' configuration of the configured web server, (in the above example, /volume1/Media), so the 'addpath' will be only 'Movie'. and this option is invalid for global actors thumbnail folder.