Integration test for disk provisioning

We need an integration test that would to validate that running pmanager.py with a certain partitioning json on a system with a corresponding layout of block devices will result in the partitions with the expected sizes and labels being created, the expected file systems formatted, and the expected entries added to /etc/fstab.

Every test case definition would consist of three parts:
- spaces json to be registered with the test cobbler server
- definition of block device layout for a VM booted from the test cobbler server
- validation script to be executed inside the VM