SG is failed to connect to CBS with x509 cert auth

SG 2.7.0 is not able to connect to CBS with x509 cert auth. Connection is working fine with password base auth.

Environment: 

SG 2.7.0-137

CBS 6.5.0-4821

CBL (iOS) - 2.7.0-91

Steps to Reproduce:

1. Install CBS and use gen_keystore.sh to install and generate certs for x509 based auth.Example command: ./gen_keystore.sh 172.16.1.205 travel-sample
2. Install SG and use below sync_gateway.json 

   {

   "adminInterface": "0.0.0.0:4985",

   "compressResponses": false,

   "databases": {

   "db": {

   "allow_conflicts": false,

   "bucket": "travel-sample",

   "cacertpath": "/home/sync_gateway/certs/ca.pem",

   "certpath": "/home/sync_gateway/certs/chain.pem",

   "enable_shared_bucket_access": true,

   "import_docs": "continuous",

   "keypath": "/home/sync_gateway/certs/pkey.key",

   "server": "couchbases://172.16.1.205:",

   "use_views": true

   }

   },

   "interface": ":4984",

   "logging": {

   "debug": {

   "enabled": true

   }

   },

   "maxFileDescriptors": 90000,

   "maxIncomingConnections": 0

   }

   }

3. Run command service sync_gateway start

Actual Result:
SG fails to start and throws below error -

2019-11-20T12:40:27.746+05:30 ==== Couchbase Sync Gateway/2.7.0(137;05d5126) EE ====

2019-11-20T12:40:27.746+05:30 ==== Couchbase Sync Gateway/2.7.0(137;05d5126) EE ====

2019-11-20T12:40:27.865+05:30 [ERR] cbgt index creation failed: manager_api: failed to connect to or retrieve information from source, sourceType: couchbase, sourceName: travel-sample, sourceUUID: e56f6f4890b825fcabafdf1c1c2d0f4c, err: gocouchbase_helper: CouchbaseBucket connection failed, server: https://172.16.1.205:18091, poolName: default, bucketName: travel-sample, sourceParams: "{\"includeXAttrs\":true}", err: HTTP error 401 Unauthorized getting "https://172.16.1.205:18091/pools": , please check that your authUser and authPassword are correct and that your couchbase cluster ("https://172.16.1.205:18091") is available -- base.(*CbgtContext).StartManager() at dcp_sharded.go:286

2019-11-20T12:40:27.865+05:30 [ERR] Error opening database db: manager_api: failed to connect to or retrieve information from source, sourceType: couchbase, sourceName: travel-sample, sourceUUID: e56f6f4890b825fcabafdf1c1c2d0f4c, err: gocouchbase_helper: CouchbaseBucket connection failed, server: https://172.16.1.205:18091, poolName: default, bucketName: travel-sample, sourceParams: "{\"includeXAttrs\":true}", err: HTTP error 401 Unauthorized getting "https://172.16.1.205:18091/pools": , please check that your authUser and authPassword are correct and that your couchbase cluster ("https://172.16.1.205:18091") is available -- rest.RunServer() at config.go:1020

Expected Result:

SG should be able to connect to CBS with x509 cert without any error

Logs :

Available in attachment fields

Steps to generate Certs and installed in CBS:

1. Download all the files available here - https://github.com/couchbaselabs/mobile-testkit/tree/master/resources/x509_cert_gen

2. Add CBS IP at the last line of openssl-san.cnf

(venv) LFC:certs lfc$ cat openssl-san.cnf 

[req]

x509_extensions = v3_req

distinguished_name = req_distinguished_name

[req_distinguished_name]

[ v3_req ]

# Extensions to add to a certificate request

basicConstraints = CA:true

keyUsage = nonRepudiation, digitalSignature, keyEncipherment

subjectAltName = @alt_names

[alt_names]

IP.1 = 172.16.1.205

3. Create a user "travel-sample" in CBS with "Full Admin" access

4. run command  ./gen_keystore.sh <CBS_IP> <CBS_USERNAME> <CBS_HOST_SSH_PASSWORD>

 ./gen_keystore.sh 172.16.1.205 travel-sample couchbase