crypto: allow multiple KES endpoints (#10383)

This commit addresses a maintenance / automation problem when MinIO-KES
is deployed on bare-metal. In orchestrated env. the orchestrator (K8S)
will make sure that `n` KES servers (IPs) are available via the same DNS
name. There it is sufficient to provide just one endpoint.

cmd/crypto/retry.go

@@ -23,7 +23,6 @@ import (
 const (
 	retryWaitMin = 500 * time.Millisecond // minimum retry limit.
 	retryWaitMax = 3 * time.Second        // 3 secs worth of max retry.
-	retryMax     = 2
 )
 
 // LinearJitterBackoff provides the time.Duration for a caller to