vmm: Improve handling of shared memory backing

As huge pages are always MAP_SHARED then where the shared memory would
be checked (for vhost-user and local migration) we can also check
instead for huge pages.

The checking is also extended to cover the memory zones based
configuration as well.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vmm/src/lib.rs

@@ -1606,12 +1606,11 @@ impl Vmm {
             .unwrap()
             .lock()
             .unwrap()
-            .memory
-            .shared
+            .backed_by_shared_memory()
             && send_data_migration.local
         {
             return Err(MigratableError::MigrateSend(anyhow!(
-                "Local migration requires shared memory enabled"
+                "Local migration requires shared memory or hugepages enabled"
             )));
         }