Make squid tests time-independent

Several squid tests were hardcoded to rely on data for October
2012. However, SquidCountArchive.pl refuses to run for dates older
than a year. Hence, the tests did no longer pass. The tests are now time
independent by using the 1st, 2nd, and 3rd day of the previous month.


Card: Analytics 1321
Bug: 58576
Change-Id: I4bf3d54c35665bd9ebec53ce9658141fa9a1983b