Fix CI after #3870 (#3872)

## Motivation

#3870 was incomplete and CI didn't catch it

## Proposal

Bring back the logic to diversify local rocksdb directories when testing

## Test Plan

CI

Author: ma2bd

.github/workflows/scylladb.yml

@@ -11,6 +11,7 @@ on:
       - 'toolchains/**'
       - 'linera-views/**'
       - 'linera-storage/**'
+      - 'linera-service/src/storage.rs'
       - 'docker_scylla/**'
   workflow_dispatch:
 

linera-service/src/cli_wrappers/local_net.rs

@@ -683,10 +683,15 @@ impl LocalNet {
     }
 
     async fn run_server(&mut self, validator: usize, shard: usize) -> Result<Child> {
-        let storage = self
+        let mut storage = self
             .initialized_validator_storages
             .get(&validator)
-            .expect("initialized storage");
+            .expect("initialized storage")
+            .clone();
+
+        // For the storage backends with a local directory, make sure that we don't reuse
+        // the same directory for all the shards.
+        storage.storage_config.maybe_append_shard_path(shard)?;
 
         let mut command = self.command_for_binary("linera-server").await?;
         if let Ok(var) = env::var(SERVER_ENV) {

linera-service/src/storage.rs

@@ -123,6 +123,24 @@ pub enum StorageConfig {
     },
 }
 
+impl StorageConfig {
+    pub fn maybe_append_shard_path(&mut self, _shard: usize) -> std::io::Result<()> {
+        match self {
+            #[cfg(all(feature = "rocksdb", feature = "scylladb"))]
+            StorageConfig::DualRocksDbScyllaDb {
+                path_with_guard,
+                spawn_mode: _,
+                uri: _,
+            } => {
+                let shard_str = format!("shard_{}", _shard);
+                path_with_guard.path_buf.push(shard_str);
+                std::fs::create_dir_all(&path_with_guard.path_buf)
+            }
+            _ => Ok(()),
+        }
+    }
+}
+
 /// The description of a storage implementation.
 #[derive(Clone, Debug)]
 #[cfg_attr(any(test), derive(Eq, PartialEq))]