feat(prod): add ipfabric virtual machine configuration

Adds the 'ipfabric' instance to the production virtual_machines inventory.
This provisions the server with 8 cores, 16GB memory, and 128GB disk
assigned to IP 192.168.1.162.

terraform/prod/terraform.tfvars

@@ -42,6 +42,15 @@ virtual_machines = {
     ip      = "192.168.1.161"
     gateway = "192.168.1.254"
     tags    = ["netlab"]
+  },
+  "ipfabric" = {
+    os      = "ipfabric"
+    cores   = 8
+    memory  = 16384
+    disk_gb = 128
+    ip      = "192.168.1.162"
+    gateway = "192.168.1.254"
+    tags    = ["ipfabric", "netlab"]
   }
 }