DTT2 - Allocator's Vagrant provider creates VMs with the same hostname

[mhamra]

Target version	Related issue	Related PR/dev branch
4.9.0	#5193

Description

When a workflow file creates two instances of the same operating system, the hostname is duplicated in the environment, generating side effects problems. See this comment for an example.

To avoid duplication, the allocator must assign the Vagrant virtual machine's name to the VM's hostname.