ci: use owners on memcheck workflow local network

With the new `--owner-prefix` argument available on the `local run` command and the local testnet
action updated for this, we can use it in the `memcheck` workflow to specify that nodes should be
assigned the owners "node_1", "node_2", and so on.

.github/workflows/memcheck.yml

@@ -81,13 +81,14 @@ jobs:
         uses: maidsafe/sn-local-testnet-action@main
         with:
           action: start
+          build: true
+          faucet-path: target/release/faucet
           interval: 2000
+          join: true
           node-path: target/release/safenode
-          faucet-path: target/release/faucet
+          owner-prefix: node
           platform: ubuntu-latest
           set-safe-peers: false
-          join: true
-          build: true
 
       # In this case we did *not* want SAFE_PEERS to be set to another value by starting the testnet
       - name: Check SAFE_PEERS was not changed

sn_node_manager/src/local.rs

@@ -416,10 +416,8 @@ fn get_node_owner(
 ) -> Option<String> {
     if let Some(prefix) = owner_prefix {
         Some(format!("{}_{}", prefix, number))
-    } else if let Some(owner) = owner {
-        Some(owner.clone())
     } else {
-        None
+        owner.clone()
     }
 }