Prevent 2 parallel open orders through forceentry

this leads to forgetting the prior order

closes #7765

tests/rpc/test_rpc.py

@@ -1066,6 +1066,11 @@ def test_rpc_force_entry(mocker, default_conf, ticker, fee, limit_buy_order_open
     trade = rpc._rpc_force_entry(pair, 0.0001, order_type='limit', stake_amount=0.05)
     assert trade.stake_amount == 0.05
     assert trade.buy_tag == 'force_entry'
+    assert trade.open_order_id == 'mocked_limit_buy'
+
+    freqtradebot.strategy.position_adjustment_enable = True
+    with pytest.raises(RPCException, match=r'position for LTC/BTC already open.*open order.*'):
+        rpc._rpc_force_entry(pair, 0.0001, order_type='limit', stake_amount=0.05)
 
     # Test not buying
     pair = 'XRP/BTC'