Inconsistent first-interval start times

[alistairking]

I haven't checked the code yet, but it seems that it is possible (based on the interim files I have on disk) that when corsarowdcap generates files for the first interval there can be different times between threads:

ucsd-nt-reactive.1563211595.pcap.gz--0  ucsd-nt-reactive.1563211595.pcap.gz--6
ucsd-nt-reactive.1563211595.pcap.gz--2  ucsd-nt-reactive.1563211596.pcap.gz--1
ucsd-nt-reactive.1563211595.pcap.gz--4  ucsd-nt-reactive.1563211596.pcap.gz--3
ucsd-nt-reactive.1563211595.pcap.gz--5  ucsd-nt-reactive.1563211596.pcap.gz--7

I guess this is because the first interval start time is based on the first packet observed, which can be slightly different between threads.