Fixes #116: AT should use default authority from PBC, when authority not provided
Fixes #116: AT should use default authority from PBC, when authority not provided

AzureAD/microsoft-authentication-library-for-objc,AzureAD/microsoft-authentication-library-for-objc,AzureAD/microsoft-authentication-library-for-objc,AzureAD/microsoft-authentication-library-for-objc,AzureAD/microsoft-authentication-library-for-objc