VM Runner: use default on option parser for port and username

Signed-off-by: NCleber Rosa <crosa@redhat.com>

optional_plugins/runner_vm/avocado_runner_vm/__init__.py

@@ -455,9 +455,10 @@ class VMCLI(CLI):
         vm_parser.add_argument('--vm-port', dest='vm_port',
                                default=22, type=int,
                                help=('Specify the SSH port number to login on '
-                                     'VM. Current: 22'))
+                                     'VM. Default: %(default)s'))
         vm_parser.add_argument('--vm-username', default=getpass.getuser(),
-                               help='Specify the username to login on VM')
+                               help=('Specify the username to login on VM. '
+                                     'Default: %(default)s'))
         vm_parser.add_argument('--vm-password',
                                default=None,
                                help='Specify the password to login on VM')