lib: fix dnode_create to use correct libyang function.

lib: fix dnode_create to use correct libyang function.

The previous use of `lyd_new_path()` returns the first node created, rather
than the xpath target node. The code is lucky in the sense that it is
normally only creating a single node rather than a branch. Fix this to
use `lyd_new_path2()` which returns the target node to actually implement
the semantics expected by callers of `dnode_create()` (i.e., returning the
newly created target node).

Signed-off-by: Christian Hopps <chopps@labn.net>