3006 VERIFY[S,U,P] and ASSERT[S,U,P] frequently check if first argument is zero

*** 527,537 ****
          /*
           * Print out the freelist entries in both encoded and decoded form.
           */
          alloc = 0;
          for (offset = 0; offset < smo->smo_objsize; offset += sizeof (entry)) {
!                 VERIFY3U(0, ==, dmu_read(os, smo->smo_object, offset,
                      sizeof (entry), &entry, DMU_READ_PREFETCH));
                  if (SM_DEBUG_DECODE(entry)) {
                          (void) printf("\t    [%6llu] %s: txg %llu, pass %llu\n",
                              (u_longlong_t)(offset / sizeof (entry)),
                              ddata[SM_DEBUG_ACTION_DECODE(entry)],
--- 527,537 ----
          /*
           * Print out the freelist entries in both encoded and decoded form.
           */
          alloc = 0;
          for (offset = 0; offset < smo->smo_objsize; offset += sizeof (entry)) {
!                 VERIFY0(dmu_read(os, smo->smo_object, offset,
                      sizeof (entry), &entry, DMU_READ_PREFETCH));
                  if (SM_DEBUG_DECODE(entry)) {
                          (void) printf("\t    [%6llu] %s: txg %llu, pass %llu\n",
                              (u_longlong_t)(offset / sizeof (entry)),
                              ddata[SM_DEBUG_ACTION_DECODE(entry)],
*** 1186,1196 ****
          dmu_buf_t *db;
  
          if (dump_opt['d'] < 3)
                  return;
  
!         VERIFY3U(0, ==, dmu_bonus_hold(os, obj, FTAG, &db));
          bt = db->db_data;
          zdb_nicenum(bt->bt_bytes, bytes);
          (void) printf("\n    %s: %llu datasets, %s\n",
              name, (unsigned long long)(bt->bt_end - bt->bt_begin), bytes);
          dmu_buf_rele(db, FTAG);
--- 1186,1196 ----
          dmu_buf_t *db;
  
          if (dump_opt['d'] < 3)
                  return;
  
!         VERIFY0(dmu_bonus_hold(os, obj, FTAG, &db));
          bt = db->db_data;
          zdb_nicenum(bt->bt_bytes, bytes);
          (void) printf("\n    %s: %llu datasets, %s\n",
              name, (unsigned long long)(bt->bt_end - bt->bt_begin), bytes);
          dmu_buf_rele(db, FTAG);
*** 2271,2281 ****
              count_block_cb, &zcb, NULL);
          (void) bpobj_iterate_nofree(&spa->spa_dsl_pool->dp_free_bpobj,
              count_block_cb, &zcb, NULL);
          if (spa_feature_is_active(spa,
              &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY])) {
!                 VERIFY3U(0, ==, bptree_iterate(spa->spa_meta_objset,
                      spa->spa_dsl_pool->dp_bptree_obj, B_FALSE, count_block_cb,
                      &zcb, NULL));
          }
  
          if (dump_opt['c'] > 1)
--- 2271,2281 ----
              count_block_cb, &zcb, NULL);
          (void) bpobj_iterate_nofree(&spa->spa_dsl_pool->dp_free_bpobj,
              count_block_cb, &zcb, NULL);
          if (spa_feature_is_active(spa,
              &spa_feature_table[SPA_FEATURE_ASYNC_DESTROY])) {
!                 VERIFY0(bptree_iterate(spa->spa_meta_objset,
                      spa->spa_dsl_pool->dp_bptree_obj, B_FALSE, count_block_cb,
                      &zcb, NULL));
          }
  
          if (dump_opt['c'] > 1)