linux: Disable sandbox for hotplug device
linux: Disable sandbox for hotplug device

When sandbox is enabled, forking a process for hotplug device
is failure, the error message is:
Failed to fork jail process: Attempt to call fork() while
multithreaded.

This means minijail couldn't fork a new process for added device
when vm has started, so disable sandbox for hotplug device.

BUG=b:185084350
TEST=Boot a guest and hotplug vfio pci device repeatedly

Change-Id: I2983399f41a44984a113c9846aff93fd978a02b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2955581
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>
Commit-Queue: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

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