LinuxDiagnostic - Error: Storage credential validation for table storage failed

I have followed the official [doc](https://docs.microsoft.com/en-us/azure/virtual-machines/extensions/diagnostics-linux#sample-installation) to install LinuxDiagnostic 3.0 using azure cli on a Marketplace RHEL 7.6 VM, but getting the error below:

## Error:
```
ERROR:CalledProcessError. Error Code is 1
ERROR:CalledProcessError. Command string was SSL_CERT_FILE=/etc/pki/tls/cert.pem SSL_CERT_DIR=/etc/pki/tls/certs /usr/local/lad/bin/mdsd -v -c /var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDia
gnostic-3.0.121/xmlCfg.xml
ERROR:CalledProcessError. Command result was 2019-07-02T01:01:52.3659280Z: Not all GCS env vars are defined. Missing 6: MONITORING_GCS_ENVIRONMENT MONITORING_GCS_ACCOUNT MONITORING_GCS_REGION MONI
TORING_GCS_CERT_CERTFILE MONITORING_GCS_CERT_KEYFILE MONITORING_GCS_STORAGE_RESOURCE_TAG_TYPE. GCS won't be used.
ERROR:Parse reported these messages:
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(3) Error: Storage credential validation for table storage failed: Server failed to authenticate the request. Ma
ke sure the value of Authorization header is formed correctly including the signature.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(18) Fatal: AddMonikerEventInfo() failed: No default credential is found.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(25) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(31) Fatal: AddMonikerEventInfo() failed: No default credential is found.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(45) Fatal: AddMonikerEventInfo() failed: No default credential is found.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(60) Fatal: AddMonikerEventInfo() failed: No default credential is found.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(70) Fatal: AddMonikerEventInfo() failed: No default credential is found.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(83) Fatal: AddMonikerEventInfo() failed: No default credential is found.
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: No default credentials were defined
ERROR:/var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml(97) Error: does not define subelement
```

Review the linked LinuxDiagnostic installation documentation and the generated /var/lib/waagent/Microsoft.Azure.Diagnostics.LinuxDiagnostic-3.0.121/xmlCfg.xml configuration. Start by examining the /usr/local/lad/bin/mdsd command output and its storage credential validation errors. Done means identifying the cause of the failed authentication and confirming installation without the reported credential and default-credential errors.

Written by the indexing model from the issue text.