[Upgrade] : Rebalance failures and Failover during upgrade causes infinite pod creation and addition to cluster

Cluster Setup

• Kind cluster locally run on Mac
• 2 nodes with all services
• 1 bucket
• Initial Cluster version : 7.0.5-7659
• Upgrade Cluster version : 7.2.3-6705

Steps taken in the scenario

• Created a cluster
• Created 1 bucket
• Issued an upgrade from 7.0.5-7659 to 7.2.3-6705 using swap rebalance
• Swap rebalance fails 
• One of the nodes in version 7.0.5 is failed over by the operator due to memcached crash
• Further a new pod is spun up and added to cluster. - Rebalance fails
• New pods are created infinitely in a loop and added to cluster and rebalance continues to fail.

Operator logs : 

 https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/cbopinfo-20240722T132821+0530.tar.gz

Cluster logs : 
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0000.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0001.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0002.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0003.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0004.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0005.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0006.cb-example.default.svc.zip
https://cb-engineering.s3.amazonaws.com/upgrade_pod_loop/collectinfo-2024-07-22T075306-ns_1%40cb-example-0007.cb-example.default.svc.zip

 The cao tool and operator images were built locally on this commit

commit c2e920ddbcfa9b4819d47ad81d0a35c359dd1dc6 (HEAD -> master, origin/master, origin/HEAD)

Author: usamah jassat <usamah.jassat@couchbase.com>

Date:   Wed Jul 17 15:11:19 2024 +0100    K8S-3581: don't attempt backend migration when rebalance required

    Change-Id: I2d2b6d6d4f8dbb0a30db5bd54a05631d17631eee

    Reviewed-on: https://review.couchbase.org/c/couchbase-operator/+/212890

    Reviewed-by: Yusuf Ramzan <yusuf.ramzan@couchbase.com>

    Tested-by: Build Bot <build@couchbase.com>