METRON-2360 BRO-PLUGIN: does not build with 3.2.1

[ottobackwards]

Cleanup namespace and includes change to newer zeek.

NOTE: new zeek does not like our pcaps used with docker testing.

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This change is 

[JonZeolla]

Tests are broken because diff isn't installed in our zeek docker image; we need to add diffutils. Since it's only required for the tests which are run during zkg install, I suggest throwing it in the zkg RUN block. After doing that I was able to get e2e all the way to the expected error due to the fix for zeek/zeek#977:

1258563753.320650 fatal error: failed to read a packet from /root/data/example-traffic/exercise-traffic.pcap: truncated dump file; tried to read 1434 captured bytes, only got 415

[JonZeolla]

+1 visual inspection and tested e2e with 3.2.1 and 3.1.5