**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.


{
    bool expected = false;
    if (!start_no_users_thread_called.compare_exchange_strong(expected, true))
        return;
    if (is_temporary)
    {
        std::lock_guard no_users_thread_lock(no_users_thread_mutex);
        if (shutdown_called)
            return;
        if (no_users_thread.joinable())
        {
            {
                std::lock_guard lock(no_users_thread_wakeup_mutex);
                no_users_thread_wakeup = true;
                no_users_thread_condition.notify_one();
            }
            no_users_thread.join();
        }
        {
            std::lock_guard lock(no_users_thread_wakeup_mutex);
            no_users_thread_wakeup = false;
        }
        if (!is_dropped)
            no_users_thread = std::thread(&StorageLiveView::noUsersThread,
                std::static_pointer_cast<StorageLiveView>(shared_from_this()), timeout);
    }
    start_no_users_thread_called = false;
}
void StorageLiveView::startup()