qemu.test: Add a host nic bonding test case

This case will create a bonding bridge in host with at lease two
physical interface and start a guest with this bridge. Do ping and
file transfer. Notice that this case need at least two nics
in host.

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
Merge pull request #87 from ypu/nic_bonding_host

qemu.test: Add a host nic bonding test case