[Guardrails] Migration of StorageBackend from CouchStore to Magma wasn't allowed when the bucket was hitting couchstoreMinimum RR guardrail

Steps:

1. Initialise a 2 node cluster running just the KV service.
2. Configure couchstoreMinimum=40 in http://172.23.106.201:8091/settings/resourceManagement

{"bucket":{"collectionsPerQuota":{"enabled":true,"maximum":1},"dataSizePerNode":{"couchstoreMaximum":1.6,"enabled":true,"magmaMaximum":16},"residentRatio":{"couchstoreMinimum":40,"enabled":true,"magmaMinimum":1}},"coresPerBucket":{"enabled":true,"minimum":0.4},"diskUsage":{"enabled":true,"maximum":85}} 

1. Create a CouchStore bucket named 'default' with 512MB RAM per node.
2. Load data until the bucket would hit the resident ratio guardrail. After hitting the guardrail, the resident ratio of the bucket on the 2 nodes were [35.25, 35.06].
3. Tried migration of the bucket by updating the storageBackend to Magma

curl -v -X POST http://172.23.106.201:8091/pools/default/buckets/default \

-u Administrator:password \

-d storageBackend=magma 

1. Got the following error:

{"errors":{"storageBackend":"Storage mode migration is not allowed when resident ratio is below the configured minimum: 40%"

1. But since magmaMinimum is set to 1, and post migration, resident ratio of the Magma bucket would be greater than the configured minimum, the operation should be allowed.