802.15.4 - Update existing Management commands

[zephyrbot]

Reported by Gajinder Vij:

Behavioral changes as well as improvements need to be applied to existing Management commands.

(Imported from Jira ZEP-891)

[zephyrbot]

by ethan gao:

low-layer implementation change and it makes more sense in unit test while developing

[zephyrbot]

by Andrei Laperie:

This is part of 2015 version of 802.15.4 standard. Currently it is not a requirement for anybody; we will schedule an implementation later when this changes.