vm-virtio: fs: Factorize vhost-user setup

This patch factorizes the existing virtio-fs code by relying onto the
common code part of the vhost_user module in the vm-virtio crate.

In details, it factorizes the vhost-user setup, and reuses the error
types defined by the module instead of defining its own types.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/vm.rs

@@ -250,7 +250,7 @@ pub enum DeviceManagerError {
     CreateVirtioRng(io::Error),
 
     /// Cannot create virtio-fs device
-    CreateVirtioFs(vm_virtio::vhost_user::fs::Error),
+    CreateVirtioFs(vm_virtio::vhost_user::Error),
 
     /// Cannot create virtio-pmem device
     CreateVirtioPmem(io::Error),