Fix pseudofs readdir method

readdir method of pseudofs expects that the first direntry should have
index 2. This may not be true if we remove export entries due to remove
export dbus command! Use avltree_first() and skip entries that are
before the seek location.

Signed-off-by: Malahal Naineni <malahal@us.ibm.com>
Acked-by: Frank S. Filz <ffilzlnx@mindspring.com>