Tapping on the courier sync button multiple times creates multiple copies of CCAs/cargoes

[gnarea]

I accidentally tapped the sync button twice very quickly, and realised that multiple CCAs, cargoes and gRPC connections were created.

Here's an excerpt from the Android Gateway logs:

2021-01-04 16:27:37.131 16895-17702/tech.relaycorp.gateway I/rgoMessageSetWithExpiry: Generating cargo for https://frankfurt.relaycorp.cloud
2021-01-04 16:27:37.131 16895-16935/tech.relaycorp.gateway I/rgoMessageSetWithExpiry: Generating cargo for https://frankfurt.relaycorp.cloud
2021-01-04 16:27:37.440 16895-16936/tech.relaycorp.gateway I/CogRPCClient: deliverCargo next 77a184f7-274d-42dc-8c27-a209d939bb84
2021-01-04 16:27:37.450 16895-16923/tech.relaycorp.gateway I/CogRPCClient: deliverCargo next 10042654-de3c-4679-bb72-746540dddf07
2021-01-04 16:27:37.818 16895-17799/tech.relaycorp.gateway I/CogRPCClient: deliverCargo ack 77a184f7-274d-42dc-8c27-a209d939bb84
2021-01-04 16:27:37.818 16895-17801/tech.relaycorp.gateway I/CogRPCClient: deliverCargo ack 10042654-de3c-4679-bb72-746540dddf07
2021-01-04 16:27:37.820 16895-17801/tech.relaycorp.gateway I/CogRPCClient: deliverCargo complete
2021-01-04 16:27:37.821 16895-17799/tech.relaycorp.gateway I/CogRPCClient: deliverCargo complete
2021-01-04 16:27:37.855 16895-17799/tech.relaycorp.gateway I/CogRPCClient: deliverCargo ack closed
2021-01-04 16:27:37.857 16895-16936/tech.relaycorp.gateway I/CogRPCClient: Closing CogRPCClient
2021-01-04 16:27:37.863 16895-17799/tech.relaycorp.gateway I/CogRPCClient: deliverCargo ack closed
2021-01-04 16:27:37.865 16895-17704/tech.relaycorp.gateway I/CogRPCClient: Closing CogRPCClient

I also saw two active users on the courier app.