Remove group writability for analitycs files /a/squid, and /a/log

Due the group writability of files underneath /a/squid, and /a/log,
they sometimes accidentally get modified by people. Hence, we remove
the group writability flag, because it is not needed there anyways.

Bug: 63505
Change-Id: Ie32df433472a6ecca47bde8d694e0eca771185c1