share/p2p/shrexeds: Potential improper closing of streams leading to server exhaustion

[renaynay]

During testing of v0.14.0-rc1 on arabica-11, ran into issues where a bootstrapper would serve my archival FN historic EDSes in bursts of ~100 EDSes or so until it hit a point where the archival FN would fail to open a stream with the bootstrapper due to ctx deadline exceeded.

This could potentially be due to improper closing of other streams, but needs further investigation.