Don't re-walk the roots fileserver in symlink_list()

[terminalmage]

This prevents some unnecessary extra work when getting a list of
symlinks.

[ninja-]

@terminalmage would that be an improvement also for people without symbolic links in their salt trees?

[terminalmage]

@ninja- I don't think there would be a performance gain for fileservers without symbolic links. The issue as initially reported by @UtahDave involved a fileserver with a number of symlinks. Since we follow symlinks by default (unless disabled by setting fileserver_folllowsymlinks to False) when walking the fileserver directories, this results in a lot of extra work, and the thought was that this was being compounded by repeating this work in the symlink_list() function. However, I never got a chance to test that hypothesis.

Either way, even if it doesn't fully solve that problem, it will still have a positive impact when symlinks are present.

[ninja-]

Ah ok. Thanks for explaining.