Fix issue with context name clashing for accounts with no subscriptions in a tenant

[cormacpayne]

Description

Fix for #7453

Contexts that were created for an account with no subscriptions in a tenant would be given a Default name since they had no subscription to create the name from, and this Default name would clash with the existing Default context with no properties that is created initially, so the new context would be thrown out and the empty context would be returned.

The fix in the common code will create a name in the format {{TENANT_ID}} - {{ACCOUNT_ID}} in this scenario, which will avoid the clashing Default names of the contexts.

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate change log has been updated
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets:
  • the changes have gone through a cmdlet design review (Microsoft internal partners only)
  • the cmdlet markdown files were generated using the platyPS module

[cormacpayne]

Common packages created from the following PR: Azure/azure-powershell-common#85