NEX-7233 Attempting to destroy ZFS filesystem and create ZFS volume with the same name caused system panic
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>
Reviewed by: Roman Strashkin <roman.strashkin@nexenta.com>
Reviewed by: Alek Pinchuk <alek.pinchuk@nexenta.com>

*** 2169,2178 ****
--- 2169,2182 ----
                          ASSERT(RW_READ_HELD(&ddv->sdev_contents));
                          if (rw_tryupgrade(&ddv->sdev_contents) == 0) {
                                  rw_exit(&ddv->sdev_contents);
                                  rw_enter(&ddv->sdev_contents, RW_WRITER);
                          }
+ 
+                         if (SDEVTOV(dv)->v_type == VDIR)
+                                 (void) sdev_cleandir(dv, NULL, SDEV_ENFORCE);
+ 
                          sdev_cache_update(ddv, &dv, nm, SDEV_CACHE_DELETE);
                          rw_downgrade(&ddv->sdev_contents);
                          SDEV_RELE(dv);
                          dv = NULL;
                          goto lookup_create_node;