Fix serialization issue

[kober32]

When we make a token-based request that will be serialized and we don't have a token yet, it creates a cycle, where:

• the whole request is put into a serial queue
• inside this request, a token is requested
• if the token is not cached, it's requested from the server
• this request is placed inside the serial queue
• this creates a deadlock on the queue and the whole PowerAuth instance is blocked and needs to be killed