Add volume type configuration parameter

[vkryuchenko]

In connection with the announcement of the transition to a new type of block storage, it became necessary to create images of virtual machines created using the sbs_volume block storage type.
However, in the plugin configuration, it is impossible to change the volume type, since the code specifies the bssd type without the ability to influence it in any way by passing the corresponding parameter.

[Codelax]

Hi, thanks for your interest with the provider. We're in the process of completing support of sbs volumes in our main tools.
This change will be coming shortly in the packer provider.