previousVersion link check is incorrect if same day publication

[plehegar]

specberus establishes if the previous version is correct by checking the bodies:
[[
else if (bodies[0] !== bodies[1]) {
]]
lib/rules/headers/dl.js

with bodies[0] coming from latest version
and bodies[1] coming from previousVersion link in the requested publication

However, if the document is published twice the same day through echidna, we need to use for bodies[0] a previous day version, not the latest version...