Add test for virsh send-key

```
  NAME
    send-key - Send keycodes to the guest

  SYNOPSIS
    send-key <domain> [--codeset <string>] [--holdtime <number>] {[--keycode] <string>}...

  DESCRIPTION
    Send keycodes (integers or symbolic names) to the guest

  OPTIONS
    [--domain] <string>  domain name, id or uuid
    --codeset <string>  the codeset of keycodes, default:linux
    --holdtime <number>  the time (in milliseconds) how long the keys will be held
    [--keycode] <string>  the key code

```

Signed-off-by: Kyla Zhang <weizhan@redhat.com>