pathbar: Handle webdav where is the root is a path

pathbar: Handle webdav where is the root is a path

Our webdav server has a root which is davs://mynextcloud/remote.php/webdav
When once creates a GFile out of or out of a subdirectory, and one call
g_file_get_parent(), it recurses too far up and try to query
davs://mynextcloud/remote.php which fails, resulting in a broken pathbar.

To fix that, before querying the metadata of each element of the path,
I query the "enclosing mount", then use it's root to compare the GFile
against.

With the right GMount, we can also fix the icon drawing code in the
pathbar for network drives.