Fix/sniffer subsystem

I have enhanced the way ooniprobe captures the packets when the pcapinclude option is activated in the config.
In the latests commits i have also consolidated the filenames of the yamloo reports with the generate_filename function to have the same basename in the report and the pcap but with different extension. I think that this feature is convinient to allow an easy development of a hypotetical script that would analyze the results of the nettests when some of them have pcaps.