Fix base_test after gopacket change.
Fix base_test after gopacket change.

Strange use of anonymous struct in base_test broke with introduction of change
in gopacket (https://github.com/google/gopacket/commit/7dcbd21d9dbad10aab15a8854bb0a26c26047c9e introduced InterfaceIndex into gopacket.CaptureInfo).

gconnell/stenographer,gconnell/stenographer,google/stenographer,dcode/stenographer,dcode/stenographer,google/stenographer,google/stenographer,dcode/stenographer,gconnell/stenographer