virttest.utils_net: Add some methods to manage guest nic's ip

This patch add a new method to get guest nic ip, support both
windows and linux guest, also add a method to renew guest ip
support both windows and linux guest.

Signed-off-by: Yunping Zheng <yunzheng@redhat.com>
virttest.virt_vm: some modifications of wait_for_get_address()

This patch modified the method of wait_for_get_address, the new method
will try to renew guest nic ip, and try to get guest ip by serial console,
instead of raising error when timeout. will raise error if both above
try failed.

Signed-off-by: Yunping Zheng <yunzheng@redhat.com>
virttest.virt_vm: using wait_for_get_address to get guest address

We suffer a lot when autotest can't log into guest, but the guest actually
have an effect ip.
Using wait_for_get_address, will try to renew guest ip and get guest ip by
serial console when it can not guest get guest address by address_cache.

Signed-off-by: Yunping Zheng <yunzheng@redhat.com>
Merge pull request #1424 from autotest/1393

Remake of PR 1393