Blockstreamer node is not always visible in gossip

[mvines]

STR:

1. Figure the IP addresses of the bootstrap leader and blockstreamer testnet nodes from the latest "testnet-beta" run at https://buildkite.com/solana-labs/testnet-management/builds?branch=v0.12
2. Run the following for both bootstrap leader and blockstreamer:

$ set ip=<node public ip>
$ RUST_LOG=info solana-bench-tps --converge-only --num-nodes 100000 --network $ip:8001

Observe that the blockstreamer node isn't gossiping with anybody, and the bootstrap leader doesn't know about the blockstreamer node.

This breaks:

1. The blockexplorer
2. Any RPC requests sent to the blockstreamer node (which is the public API face of the beta testnet).

Unclear if #3442 is related.

[mvines]

Here's a quick way to check if this issue is not occurring:

$ RUST_LOG=solana=info solana-bench-tps --converge-only --num-nodes 5 --network $(dig +short beta.testnet.solana.com):8001

This uses the blockstreamer node as the gossip entry point, and looks for the 5 nodes (1 bootstrap leader, 3 validators, 1 blockstreamer)

[mvines]

Once #3705 lands we should be able to easily see if this issue still manifests on master

[mvines]

As of #3705, this issue will show up as a ./net.sh sanity failure so closing this as a dup of #2314