schema REFACTOR avoid code duplication and improve code readability
schema REFACTOR avoid code duplication and improve code readability

lysc_node_children_p() and lysc_node_children_full() were wery similar,
refactoring should avoid code duplication and emphasis the differences
between the functions.

Fixes #1352

CESNET/libyang,sartura/libyang,sartura/libyang,sartura/libyang,sartura/libyang,CESNET/libyang,sartura/libyang,sartura/libyang