Only create the virtio-console read thread once
Only create the virtio-console read thread once

The virtio-console device implementation was losing track of the host
input stream when it reset. This change only creates the read thread
once and reuses it for all worker threads.

Test: Run with a virtio-console device that resets
Bug: b/208540565
Change-Id: I6abcd35a7e7664f2bbdc0d977c2eacad49e50378
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3309208
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Reviewed-by: Chirantan Ekbote <35787c0e27de5c48735e07f8324823b765e8bcbc@chromium.org>
Commit-Queue: Cody Schuffelen <7618f12f8c1ef40a3c8bf8909fc72185c1ec8ce8@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm