bug: export not drop temp table

[lianxmfor]

To reproduce:

$ oomcli init
$ cd ~/github.com/oomstore/
$ cd oomcli/test/
$ oomcli apply -f /tmp/tmp/meta.yaml
applied
$ oomcli get meta entity -o yaml
items:
  - kind: Entity
    name: user
    description: user
    groups:
      - name: user-click
        category: stream
        snapshot-interval: 1s
        description: user click post feature
        features:
          - name: last_5_click_posts
            value-type: string
            description: user last 5 click posts
          - name: number_of_user_starred_posts
            value-type: int64
            description: number of posts that users starred today
  - kind: Entity
    name: device
    description: device
    groups:
      - name: phone
        category: batch
        description: phone
        features:
          - name: price
            value-type: int64
            description: price
          - name: model
            value-type: string
            description: model
$ oomcli import --group phone --input-file device.csv --description 'test data'
importing features ...
succeeded
RevisionID: 2
$ oomcli export --feature phone.price,phone.model --unix-milli 1644805636602
+--------+-------------+-------------+
| device | phone.price | phone.model |
+--------+-------------+-------------+
+--------+-------------+-------------+
$ litecli /tmp/tmp/oomstore.db
Version: 1.7.0
Mail: https://groups.google.com/forum/#!forum/litecli-users
GitHub: https://github.com/dbcli/litecli
/tmp/tmp/oomstore.db> .tables ;
+---------------------------------------+
| name                                  |
+---------------------------------------+
| entity                                |
| feature                               |
| feature_group                         |
| feature_group_revision                |
| offline_batch_snapshot_2_1            |
| offline_batch_snapshot_2_2            |
| online_stream_1                       |
| tmp_export_entity_1644819331541386794 |
+---------------------------------------+
Time: 0.008s
/tmp/tmp/oomstore.db>