virttest.qemu_monitor: Make send_args_cmd return output in list if multi command used

Before send_args_cmd in qmp will return output in list when multi commands
used, but send_args_cmd in human monitor return string joined by ";".

This patch make both of them return output in list.

If single command used, do not return  its output in list for compatibility

Signed-off-by: Feng Yang <fyang@redhat.com>
virttest.qemu_monitor: Add block resize function in qemu_monitor

Add a function for block resize for both hmp and qmp monitor class

Signed-off-by: Yiqiao Pu <ypu@redhat.com>
virttest.qemu_monitor: Update send_args_cmd command.

Fix bug that it could not return correct result for some commands.
Also update the place for command line recording.

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