vm-migration: Don't store the id as part of Snapshot structure

The information about the identifier related to a Snapshot is only
relevant from the BTreeMap perspective, which is why we can get rid of
the duplicated identifier in every Snapshot structure.

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

virtio-devices/src/vhost_user/blk.rs

@@ -381,7 +381,7 @@ impl Snapshottable for Blk {
     }
 
     fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        self.vu_common.snapshot(&self.id(), &self.state())
+        self.vu_common.snapshot(&self.state())
     }
 }
 impl Transportable for Blk {}

virtio-devices/src/vhost_user/fs.rs

@@ -651,7 +651,7 @@ impl Snapshottable for Fs {
     }
 
     fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        self.vu_common.snapshot(&self.id(), &self.state())
+        self.vu_common.snapshot(&self.state())
     }
 }
 impl Transportable for Fs {}

virtio-devices/src/vhost_user/mod.rs

@@ -430,15 +430,11 @@ impl VhostUserCommon {
         }
     }
 
-    pub fn snapshot<T>(
-        &mut self,
-        id: &str,
-        state: &T,
-    ) -> std::result::Result<Snapshot, MigratableError>
+    pub fn snapshot<T>(&mut self, state: &T) -> std::result::Result<Snapshot, MigratableError>
     where
         T: Versionize + VersionMapped,
     {
-        let snapshot = Snapshot::new_from_versioned_state(id, state)?;
+        let snapshot = Snapshot::new_from_versioned_state(state)?;
 
         if self.migration_started {
             self.shutdown();

virtio-devices/src/vhost_user/net.rs

@@ -418,7 +418,7 @@ impl Snapshottable for Net {
     }
 
     fn snapshot(&mut self) -> std::result::Result<Snapshot, MigratableError> {
-        self.vu_common.snapshot(&self.id(), &self.state())
+        self.vu_common.snapshot(&self.state())
     }
 }
 impl Transportable for Net {}