* Fix stale admin lock metric when lock expires and is reacquired (#8857)
When a lock expired without an explicit unlock and a different client
acquired it, the old client's metric was never cleared, causing
multiple clients to appear as simultaneously holding the lock.
* Use DeleteLabelValues instead of Set(0) to remove stale metric series
Avoids cardinality explosion from accumulated stale series when
client names are dynamic.
* remove old raft servers if they don't answer to pings for too long
add ping durations as options
rename ping fields
fix some todos
get masters through masterclient
raft remove server from leader
use raft servers to ping them
CheckMastersAlive for hashicorp raft only
* prepare blocking ping
* pass waitForReady as param
* pass waitForReady through all functions
* waitForReady works
* refactor
* remove unneeded params
* rollback unneeded changes
* fix
