Increment progress on skipped files

With the latest update, already existing symlinks are not overwritten, but rather just skipped:

https://github.com/Stex/plex_symlinker/blob/310b4667f55461245407bd823570383d72bc37d5/lib/plex_symlinker/operation.rb#L80

As the `increment` call is after the early return, the progress bar can appear stuck, this should be moved up.