Decide eviction group ties based on time.

This corrects a bug the case of tying group size where the code may
fail to select the group with the newest member. Since newest time
is the final selection criteria, failing to break ties on it
on the step before can undermine the final selection.

Tied netgroups are very common.

(cherry picked from commit 8e09f914f8ec66301257358b250e9a61befadd95)