vmm: Move codebase to GuestMemoryAtomic from vm-memory

Relying on the latest vm-memory version, including the freshly
introduced structure GuestMemoryAtomic, this patch replaces every
occurrence of Arc<ArcSwap<GuestMemoryMmap> with
GuestMemoryAtomic<GuestMemoryMmap>.

The point is to rely on the common RCU-like implementation from
vm-memory so that we don't have to do it from Cloud-Hypervisor.

Fixes #735

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

vmm/src/device_manager.rs

@@ -49,6 +49,8 @@ use vm_device::interrupt::{
 };
 use vm_device::{Migratable, MigratableError, Pausable, Snapshotable};
 use vm_memory::guest_memory::FileOffset;
+#[cfg(feature = "cmos")]
+use vm_memory::GuestAddressSpace;
 use vm_memory::{Address, GuestAddress, GuestUsize, MmapRegion};
 #[cfg(feature = "pci_support")]
 use vm_virtio::transport::VirtioPciDevice;
@@ -739,7 +741,7 @@ impl DeviceManager {
                 .lock()
                 .unwrap()
                 .guest_memory()
-                .load()
+                .memory()
                 .last_addr()
                 .0
                 + 1;