Taken tasks is released back to 'ready' state after reload

[TvoroG]

Example:

• Worker takes a task
• Run package.reload()
• Task is released back to ready state.
• Worker cannot ack task

https://github.com/tarantool/queue/issues/66 https://github.com/tarantool/queue/pull/106

[LeonidVas]

The queue doesn't currently support package.reload(), but we plan to add this functionality in the future.