data tree BUGFIX check number of instances of non-list nodes
data tree BUGFIX check number of instances of non-list nodes

check that there is 0..1 leaf/container/anyxml instance in the data tree

lukasmacko/libyang,PavolVican/libyang,lukasmacko/libyang,PavolVican/libyang,PavolVican/libyang,PavolVican/libyang,PavolVican/libyang