Delete useless and wrong comments in NEC Plugin

This commit deletes useless and wrong comments in NEC Plugin, and adds
_clean_nec_ini() to Cleanup to make sure it is called.

Fixes: bug #1208716
Change-Id: I5c7950617cdf5d66f5f5cf3334bf2d5e617148eb
Merge "Delete useless and wrong comments in NEC Plugin"