Ensure proper PostgreSQL instance name appears after failover

After a failover occurs, the `--query` method found on `pgo scaledown`
and `pgo failover` could potentially show the same name for every
single replica, due to it utilizing just the prefix. This of course, is
not good when one may need to failover or scale down in the future.

This fix moves the check over to a regular expression that follows the
Kubernetes pod name.

Issue: [ch6931]

Author: Jonathan S. Katz

util/failover.go

@@ -19,7 +19,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"strings"
+	"regexp"
 
 	"github.com/crunchydata/postgres-operator/config"
 	"github.com/crunchydata/postgres-operator/kubeapi"
@@ -67,6 +67,9 @@ const (
 	// instanceReplicationInfoTypePrimary is the label used by Patroni to indicate that an instance
 	// is indeed a primary PostgreSQL instance
 	instanceReplicationInfoTypePrimary = "Leader"
+	// pgPodNamePattern pattern is a pattern used by regexp to look up the
+	// name of the pod
+	pgPodNamePattern = "%s-[0-9a-z]{10}-[0-9a-z]{5}"
 )
 
 var (
@@ -195,7 +198,18 @@ func ReplicationStatus(request ReplicationStatusRequest) (ReplicationStatusRespo
 		//
 		// This is not the cleanest way of doing it, but it works
 		for name, node := range instanceNodeMap {
-			if strings.HasPrefix(rawInstance.PodName, name) {
+			r, err := regexp.Compile(fmt.Sprintf(pgPodNamePattern, name))
+
+			// if there is an error compiling the regular expression, add an error to
+			// log log and keep iterating
+			if err != nil {
+				log.Error(err)
+				continue
+			}
+
+			// see if there is a match in the names. If it , add the name and node for
+			// this particular instance
+			if r.Match([]byte(rawInstance.PodName)) {
 				instance.Name = name
 				instance.Node = node
 				break