virttest.virt_vm: Simple wait_for_get_address() function

1) It broken our timeout mechanism.
2)The more important is we already have restart_gust_network() in wait_for_login(),
  so no need restart guest network in wait_for_get_address().
3) Could not get mac not always means we need restart guest network.

Signed-off-by: Feng Yang <fyang@redhat.com>
virttest.virt_vm: Do not call self.wait_for_get_address() in vm.login()

login() function is one time action. So it should not call wait_for_*()
function. Or we will have wait_for_* in wait_for_login().

Signed-off-by: Feng Yang <fyang@redhat.com>
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>
Merge pull request #1764 from FengYang/login

wait_for_login() related update
virttest.nfs: support NFS client setup

Signed-off-by: Alex Jia <ajia@redhat.com>