event/ServerSocket: do not close all listeners before rethrowing

If binding one address fails, we don't need to close all listeners.
For fatal errors, this will be done automatically and implicitly; and
for non-fatal errors (e.g. binding to the default port failed, but
there is an XDG listener), this closes the good listeners which are
supposed to be used.

Closes #2157

src/event/ServerSocket.cxx

@@ -216,7 +216,6 @@ ServerSocket::Open()
 			continue;
 
 		if (bad != nullptr && i.GetSerial() != bad->GetSerial()) {
-			Close();
 			std::rethrow_exception(last_error);
 		}
 
@@ -257,7 +256,6 @@ ServerSocket::Open()
 	}
 
 	if (bad != nullptr) {
-		Close();
 		std::rethrow_exception(last_error);
 	}
 }