When updating SENTINEL with master’s new password (command:
`SENTINEL SET mymaster auth-pass some-new-password`),
sentinel might still keep the old connection and avoid reconnecting
with the new password. This is because of wrong logic that traces
the last ping (pong) time to servers. In fact it worked fine until 8631e64
changed the condition to send ping. To resolve it with minimal risk,
let’s disconnect master and replicas once changing password/user.
Based on earlier work of yz1509.
a6bf509810