build-unit-test-docker: Update third-party packages
build-unit-test-docker: Update third-party packages

 - boost: 1.66.0 -> 1.68.0
 - googletest: 2018-06-14 -> 2018-10-11
 - json: 3.0.1 -> 3.3.0
 - libvncserver: 2018-06-20 -> 2018-10-08

Change-Id: I5daf2666218ec640b0fa53d7df29d4e569f209cf
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts