LocalFileSystem: fs.isdir fails for links that point to directories

[d-v-b]

fs.isdir fails to detect symlinked directories as directories. This can be fixed by checking if the destination of the link is a directory. Would this be desirable as a PR?

[martindurant]

Was this fixed in #608 ?

[d-v-b]

probably... I will see if my problems go away with that change

[ianthomas23]

This was indeed fixed by #608 and can be closed.

MWE:

from fsspec.implementations.local import LocalFileSystem

fs = LocalFileSystem()
fs.mkdir('/tmp/test')
fs.touch('/tmp/test/target')
fs.symlink('/tmp/test/target', '/tmp/test/link')

assert fs.islink('/tmp/test/link')

which is essentially the same as test_symlink added by that PR.