5056 ZFS deadlock on db_mtx and dn_holds
Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

*** 559,569 ****
  
          if (spa_version(dmu_objset_spa(dp->dp_meta_objset)) <
              SPA_VERSION_DELEGATED_PERMS)
                  return (SET_ERROR(EPERM));
  
!         if (dsl_dataset_is_snapshot(ds)) {
                  /*
                   * Snapshots are treated as descendents only,
                   * local permissions do not apply.
                   */
                  checkflag = ZFS_DELEG_DESCENDENT;
--- 559,569 ----
  
          if (spa_version(dmu_objset_spa(dp->dp_meta_objset)) <
              SPA_VERSION_DELEGATED_PERMS)
                  return (SET_ERROR(EPERM));
  
!         if (ds->ds_is_snapshot) {
                  /*
                   * Snapshots are treated as descendents only,
                   * local permissions do not apply.
                   */
                  checkflag = ZFS_DELEG_DESCENDENT;