qemu: clear persist flag on tap device
qemu: clear persist flag on tap device

In the scenario which tap device was not created by qemu but passed
in(e.g, with some cni plugin), there was IFF_PERSIST flag set on it,
the flag need to be cleared to make sure tap device removed cleanly
on qemu exit.

hyperhq/runv,laijs/runv,hyperhq/runv,hyperhq/runv,laijs/runv,laijs/runv