CLEANUP: connections: rename the toremove_lock to takeover_lock

This lock was misnamed and a bit confusing. It's only used for takeover
so let's call it takeover_lock.
diff --git a/src/cfgparse.c b/src/cfgparse.c
index e3f3d9f..443c406 100644
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -3571,7 +3571,7 @@
 							goto err;
 						idle_conns[i].cleanup_task->process = srv_cleanup_toremove_connections;
 						idle_conns[i].cleanup_task->context = NULL;
-						HA_SPIN_INIT(&idle_conns[i].toremove_lock);
+						HA_SPIN_INIT(&idle_conns[i].takeover_lock);
 						MT_LIST_INIT(&idle_conns[i].toremove_conns);
 					}
 				}