virttest.virt_vm: Try to login again after restart network.

So will try to restart guest network when normal login timeout.
Call login again after restart guest network.
This is also what we want when adding restart_network code.
Please refer to (7dfcc5a0f9c3b9ca28f32490e89eda5216591649 in upstream)

Signed-off-by: Feng Yang <fyang@redhat.com>
Merge restart_guest_network() and renew_guest_ip() to restart_guest_network()

Signed-off-by: Feng Yang <fyang@redhat.com>
virttest.virt_vm: Try to get guest network status when login timeout in wait_for_login().

Signed-off-by: Feng Yang <fyang@redhat.com>