Allow QEMU devices to use tap interfaces.
Allow QEMU devices to use tap interfaces.

This allows a pipeline QEMU job to set the netdevice in the
context to tap and then be able to use a hacking session.

Change-Id: I3d1d4b209866abe9249492326f3a3e290de24cb1

Linaro/lava-server,Linaro/lava-server,Linaro/lava-server,Linaro/lava-server