add patch fixing fd leak for vhost

add patch fixing fd leak for vhost

Each pause+resume operation (which is also done as part of taking a VM
snapshot) would increase the number of open file descriptors by the
number of vhost devices (e.g. network devices by default). This could
lead to crashes during backup and surely other issues once the system
limit (default 1024) was reached [0].

[0]: https://forum.proxmox.com/threads/131603/

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>