[software/VDIF_test.py] arming earlier

Just after the ADC MMCM calibration is done, the one pps shoud
arm to the GPS pps.  Then a sleep for 2 seconds so that the
internal PPS signal stabilizes.

Now that there is a stable internal pps, we can proceed to
initialize the rest of the system including headers.

An issue with this is that occasionally if the GPS pps varies
in period the startup internal pps signal could have a shortened
or extended period when arming to a new GPS pps.  This has the
effect that on some startups the packets streaming would be
stamped with a time up to a second late.  This fixes that issue
and has produced reliable time stamps.
[software/capture_32.sh] adding script for packet capture

I am adding a script that will allow the root user to capture
from tcpdump data from the R2DBE associated with the start of the
second.

This listens and captures 32 consecutive packets starting at
data frame 0 (at the start of a new second in time) on ports eth3
and eth5 of the Mark6.

This piece of code is useful for zero baseline tests and observing
signal statistics out of the R2DBE.
[software/pcap_to_vdif.py] Adding script needed by capture_32.sh

Adding script to take pcap data from tcpdump and output vdif files