Failover verification

[davissp14]

Custom failover validation process that will prevent failovers when quorum can't be met.

Notable impact:

• This will help mitigate certain split-brain scenarios that would occur during a network split.
• This will remove HA from a 2-node setup until we can properly differentiate a down node from a network split.

lax [info]repmgrd         | [2023-01-04 21:19:20] [DETAIL] /usr/local/bin/failover_validation -visible-nodes 1 -total-nodes 2
lax [info]repmgrd         | [2023-01-04 21:19:20] [INFO] output returned by failover validation command:
lax [info]repmgrd         | Unable to perform failover as quorum can not be met. Total nodes: 2, Visible nodes: 1