Fixing some inaccuracies

[cdelzotti]

Hello, I found some inaccuracies within npf :

• Some code in the zltexp design wasn't working as expected when the maximum rate had been reached and some configurations remained.
• Weirdly enough, some components were set as inactive in the packet-generating module, keeping NPF from sending packets.

[tbarbette]

It would be better to do a PR per topic

For the packet generation, it is enabled after some delay by

npf/modules/fastclick-play-single-mt.npf

Line 334 in db4d729

write fdIN{{ t }}.active true,

can you run with --show-files to see the value?

Seems ok for the ZLT. But I can't merge then :) It would be great to add a failing testcase (with an example script in integration.sh or a python unittest in integration/unittest.py) and show how it is solved here. But that's optional.