Fix cookie lib hash (#1779)
test code:
```lua
local key = "test"
local function printState()
PrintTable({
realval = sql.QueryValue( "SELECT value FROM cookies WHERE key = " .. SQLStr(key) ),
cached = cookie.GetString(key),
})
end
cookie.Set(key, 1) -- set initial value
printState() -- ok. cached but not commited so realval is nil for now
timer.Simple(31, function() -- wait cache ttl (time to live) period
-- Update cached value immediately but don't refresh cache's ttl so it's expires
-- At this point, we also schedule a commit to the DB
cookie.Set(key, 2)
-- Because the caches ttl is expired, the cookie.GetString function should request a value from the DB
-- But as we remember, in the previous step we just scheduled a value update
-- It has not been commuted so the cache will be updated with the wrong value and contain the wrong value for the next 30 seconds
printState() -- realval and cache values are both "1"
-- Wait for scheduled commit
timer.Simple(2, function()
-- As stated before, cache now and for the next 30 seconds (28 seconds) will be wrong
printState() -- We have "1" for cached value and "2" for real value in database
end)
end)
```
