Description of problem:
If connection ttl is equal to the check-period there is only 1 opportunity to validate the live / backup connection, cluster connection or replication connection.  If a system is under highload or there is a minor network delay there is a high probability of a clister split / failure due to connection timeout. 

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. Set connection-ttl or override to 30000ms and check-period to 30000 (default)
2. Add 500ms of latency to the network interface:
tc qdisc add dev lo root handle 1:0 netem delay 500msec
3. Cluster will split

Actual results:
Cluster splits causing more then 1 live server in a live / backup pair.

Expected results:
Add a WARN log recommending not setting connection-ttl / override to the same value as the check-period for the reasons noted above.

Additional info: