Fix finder on symlinks pointing to directories

When finder encountered a symlink pointing to a directory it attempted
to ignore it, but becuase Lstat returns the a *os.FileInfo for the
symlink the child.IsDir() check always returned false.  Call Stat
on the symlink to get the *os.FileInfo for the target of the symlink.

Bug: 157656545
Test: finder_test.go
Change-Id: Ie33d2e05d5c435b48e83eaeadf7b3c9816398404