Revert "Support CIDR ranges in $wgSquidServersNoPurge"

Potential performance problems

This reverts commit f1383d04b8edf1dfd355f9332ff3f154a89cc536.

Change-Id: Ie99e9ac47f34a03b4f15e64c8a7ab8af7ec5e79b
Merge "Revert "Support CIDR ranges in $wgSquidServersNoPurge"" into wmf/1.23wmf3