Fix random client failures during GC server shutdown

We need to close the GC server socket before shutting down the active
GC client connections, otherwise a client may (re)connect and get
ECONNRESET. But also handle ECONNRESET for resilience.

Fixes random failures like

  GC socket disconnected
  connecting to '/tmp/nix-shell.y07M0H/nix-test/default/var/nix/gc-socket/socket'
  sending GC root '/tmp/nix-shell.y07M0H/nix-test/default/store/kb5yzija0f1x5xkqkgclrdzldxj6nnc6-non-blocking'
  reading GC root from client: error: unexpected EOF reading a line
  1 store paths deleted, 0.00 MiB freed
  error: reading from file: Connection reset by peer

in gc-non-blocking.sh.

0 files changed, 0 insertions, 0 deletions