via-sizing/lw_azure_inventory.sh multiple sku match from tmp_map causing error

Ran this in azure cloud but there is an error calculating total_vCPU with returning multiple rows when executing `vCPU=$(grep $sku ./tmp_map | cut -d: -f2)` because of skus with _Promo suffix.

Example:

```
$ grep Standard_DS2_v2 tmp_map
Standard_DS2_v2:2
Standard_DS2_v2_Promo:2
```

I did grep for `$sku:` as a quick hack to allow me to get cpu count.