Only lock view->newzone.lock if not already locked

Only lock view->newzone.lock if not already locked

Some code paths try to lock an already locked view->newzone.lock.

For example, do_modzone() aqcuires the lock and then calls
delete_zoneconf(), that wants to acquire the same lock.

Add a parameter to delete_zoneconf() that informs the function if the
lock has already been acquired.

(cherry picked from commit 71587b0816a9458895aaa14a85539acd91afda38)