**Describe the bug**
Using `ALTER LIVE VIEW view REFRESH` results in an exception.

**How to reproduce**
* Connected to ClickHouse server version 20.8.1 revision 54438
* `CREATE TABLE` statements for all tables involved
```
clicktest :) SHOW CREATE table0

SHOW CREATE TABLE table0

┌─statement─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ CREATE TABLE default.table0
(
    `d` Date,
    `a` String,
    `b` UInt8,
    `x` String,
    `y` Int8
)
ENGINE = MergeTree()
ORDER BY d
SETTINGS index_granularity = 8192 │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

1 rows in set. Elapsed: 0.006 sec.
```
* Queries to run that lead to unexpected result
```
ClickHouse client version 20.8.1.4447 (official build).
Connecting to localhost:9000 as user default.
Connected to ClickHouse server version 20.8.1 revision 54438.

clicktest :) SET allow_experimental_live_view=1

SET allow_experimental_live_view = 1

Ok.

0 rows in set. Elapsed: 0.003 sec.

clicktest :) CREATE LIVE VIEW live1 AS SELECT * FROM table0

CREATE LIVE VIEW live1 AS
SELECT *
FROM table0

Ok.

0 rows in set. Elapsed: 0.008 sec.

clicktest :) ALTER LIVE VIEW live1 REFRESH

ALTER LIVE VIEW live1
    REFRESH

Received exception from server (version 20.8.1):
Code: 49. DB::Exception: Received from localhost:9000. DB::Exception: RWLockImpl::getLock(): RWLock is already locked in exclusive mode.

0 rows in set. Elapsed: 0.005 sec.
```
**Expected behavior**
A clear and concise description of what you expected to happen.


{
    Pipes pipes;
    for (auto & blocks_for_source : *blocks)
        pipes.emplace_back(std::make_shared<BlocksSource>(std::make_shared<BlocksPtr>(blocks_for_source), sample_block));
    return pipes;
}
BlockInputStreamPtr StorageLiveView::completeQuery(Pipes pipes)
{
    
    auto block_context = std::make_unique<Context>(global_context);
    block_context->makeQueryContext();
    auto creator = [&](const StorageID & blocks_id_global)
    {
        auto parent_table_metadata = getParentStorage()->getInMemoryMetadataPtr();
        return StorageBlocks::createStorage(
            blocks_id_global, parent_table_metadata->getColumns(),
            std::move(pipes), QueryProcessingStage::WithMergeableState);
    };
    block_context->addExternalTable(getBlocksTableName(), TemporaryTableHolder(global_context, creator));
    InterpreterSelectQuery select(getInnerBlocksQuery(), *block_context, StoragePtr(), nullptr, SelectQueryOptions(QueryProcessingStage::Complete));
    BlockInputStreamPtr data = std::make_shared<MaterializingBlockInputStream>(select.execute().getInputStream());
    
    
    
    data = std::make_shared<SquashingBlockInputStream>(
        data, global_context.getSettingsRef().min_insert_block_size_rows,
        global_context.getSettingsRef().min_insert_block_size_bytes);
    return data;
}
void StorageLiveView::writeIntoLiveView(