IO-Thread OPC-UA reconnect

[ogsadmin]

The documentation states the following:

• Once a connection is established, the client keeps the connection open and reconnects if necessary.
• If the connection fails unrecoverably (state->connectStatus is set to an error), the client is no longer usable. Create a new client if required.
• The user will have to periodically call UA_Client_run_iterate to ensure that asynchronous events are handled, including keeping a secure connection established. This is especially relevant for connection/session management and subscriptions

Currently the last two items are not correctly handled in the IOThread class. That's likely the reason why reconnect does not work reliably!

TODO: implement!

[ogsadmin]

Fixed in branch fix_reconnect