Concurrent download issues / potential timeouts

The Issue

I was able to reproduce the issues @jackrobison was seeing with concurrent downloads. To me it seems that the same peer won't be available for the 2nd of the 2 concurrent downloads, and the 2nd download won't start until the first completes. I ran a script where 2 downloads would start concurrently and then compared it to a single download - the results were consistent.

The 2nd download would never use the same peers the first did (i.e. not connect to my PC / reflector). If I ran that same download on it's own, it would. On slower connections, this would most likely cause timeouts on the 2nd download.

The first and third runs are with 2 downloads, the 2nd/4th are with 1. This was done with lbry://bitcoin and lbry://one

Starting requests
get: 3141.890ms
get 2: 25644.097ms

C:\Users\thoma\Documents\timing-scripts>node script.js
Starting requests
get: 3176.332ms

C:\Users\thoma\Documents\timing-scripts>node script.js
Starting requests
get: 3655.100ms
get 2: 25320.714ms

C:\Users\thoma\Documents\timing-scripts>node script.js

Starting requests
resolve: 163.547ms
get: 3227.946ms

Start with the timing-scripts reproduction using node script.js and compare the recorded single-download and concurrent-download timings for lbry://bitcoin and lbry://one. Investigate why the second download cannot use peers available to the first; done means concurrent downloads can access eligible peers without the observed delay or timeout risk.