Return parent node in `getNodesForPath`

Issue we're solving: Windows native WebDAV client doesn't show first file/directory in the directory listing.

Reason: first item in XML response for PROPFIND should be **current directory**.

I broke this rule previously here: https://github.com/bigcommerce-labs/sabre-dav/compare/1.8.7-alpha...1.8.7.3#diff-0a43e41da8e000bb77a423ebd27b6ba5L1514 by overriding `$nodes` variable in `lib/Sabre/DAV/Server.php:1524`

Now I remember that I did this and unfortunately forgot to fix it as everything was working fine in CyberDuck and cadaver and litmus tests were passing :-(

Now, if we're getting children by `getChildren` method, instead of returning only children, it returns **parent and children** inside of `AppendIterator`.

I'm also planning to write a blogpost / page on confluence as by this i've learnt about quite important differences in various clients & that litmus tests are not strict enough guarantee functionality across these clients.