DevTest Labs does not set ARM template parameter _artifactsLocation correctly

When DevTest Labs deploys an environment from an ARM template, it misses the trailing '/' on parameter _artifactsLocation.
So value currently looks like: `https://xxx.blob.core.windows.net/artifacts/SharePoint-AllVersions.132932726444650209/SharePoint-AllV1335581893`

This is bad: It should have the same behavior as ARM function [deployment().properties.templateLink.uri](https://docs.microsoft.com/en-us/azure/azure-resource-manager/templates/template-functions-deployment), which includes a trailing '/' at the end.
So value should looke like: `https://xxx.blob.core.windows.net/artifacts/SharePoint-AllVersions.132932726444650209/SharePoint-AllV1335581893/`

Impact on the ARM templates for DevTest Labs:
- They have to [manually add the trailing '/'](https://github.com/Azure/azure-devtestlab/blob/fe75fce0f3d4cd61ac7f9bf6a680cce345b6a6a2/Environments/SharePoint-AllVersions/azuredeploy.json#L347) to the value passed in _artifactsLocation by DevTest Labs.
- Their default value of parameter _artifactsLocation cannot / should not be `deployment().properties.templateLink.uri`, because it would not reflect the actual format of the value at deployment time.
- Since the templates cannot use `deployment().properties.templateLink.uri` as default value, this causes a validation error when using [ARM TTK](https://github.com/Azure/arm-ttk) to validate the templates syntax.