qemu.tests: fix login test fail when need_install is yes

VM paused after install finished because of option '-no-shutdown', and
env.get_vm() got a paused VM, so case will fail at wait_for_login() when
need_install is 'yes';

Signed-off-by: Xu Tian <xutian@redhat.com>
virttest.qemu_devices: Support for old qemu ide disks

Older qemu versions (RHEL6) doesn't support ide-hd and ide-cd.
Use ide-drive instead.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>