[BucketDurability]: Doc created successfully for Ephemeral bucket with bucket d_level 'persistToMajority'

Build: 6.6.0-7601

Steps to reproduce:

1. Single node cluster
2. Create a Ephemeral bucket with bucket_level_durability=persistToMajority

   ]# /opt/couchbase/bin/couchbase-cli bucket-create -c 10.112.191.101:8091 -u Administrator -p password --durability-min-level persistToMajority --bucket-type ephemeral --bucket default --bucket-ramsize 100

   SUCCESS: Bucket created

1. Insert doc into the created bucket

Expected behavior:

All doc operations should fail will the reason 'DurabilityImpossible' exception since the min_required durability is set to persistToMajority during the bucket_create

Server logs:

https://cb-jira.s3.us-east-2.amazonaws.com/logs/ephemeral_durability_create/collectinfo-2020-05-12T141854-ns_1%40cb.local.zip

Note: Creating Ephemeral bucket with persistToMajority is already a known scenario (MB-39293)