MERGE3 handles fake merge views

Under some conditions, MERGE3 handles fake merge views. After "merge", number of members that form the cluster still the same and the mergeView contains only one subgroup.

Scenario:

• Form a large cluster (1115 mbrs)
• Enable MERGE3 TRACE logging level on coordintor member (172.29.190.5)
• Reboot one machine (172.29.190.5) hosting 7 JVMs
• Coord install a new view with 1108 mbrs.

When new members join the cluster we observe a merge view formed by only one subgroup.

Coordinator log file was attached to this JIRA.