virtio: fix link up/down flag

virtio: fix link up/down flag

Type: fix

"set int state <interface> down" puts the virtio device link
down. It will not put the link in "UP" state, when
"set int state <interface up>" will be used again to change
the interface admin up. This patch fixes it.

To test:
create tap
set int state tap0 up
set int state tap0 down
sh hardware
sh int
set int state tap0 up
sh int
sh hardware

Change-Id: I3c0e31539f8a2a1e40220e7fb57eedecf408f067
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>
(cherry picked from commit 529f0e97b6064039c500adce0d54b738954b2ffa)