Revert "lowpan: Introduce new unit tests for data classes"

This reverts commit 93ea3ce9.

Reason for revert: Build failure in build 4190632 on branch `git_wear-master`.
Not all branches based on master include platform/frameworks/opt/net/lowpan.

Change-Id: I70fe6be8d71424e11a537daaa69c3f6cfae8e49d