test/e2e: put ledger to bg to avoid it getting stuck

tests/src/e2e/ledger_tests.rs

@@ -220,11 +220,13 @@ fn run_ledger_load_state_and_reset() -> Result<()> {
     ledger.exp_string("No state could be found")?;
     // Wait to commit a block
     ledger.exp_regex(r"Committed block hash.*, height: [0-9]+")?;
+    let bg_ledger = ledger.background();
     // Wait for a new epoch
     let validator_one_rpc = get_actor_rpc(&test, &Who::Validator(0));
     epoch_sleep(&test, &validator_one_rpc, 30)?;
 
     // 2. Shut it down
+    let ledger = bg_ledger.foreground();
     ledger.send_control('c')?;
     // Wait for the node to stop running to finish writing the state and tx
     // queue