test-runner: Drop options no longer supported by qemu

-nodefconfig doesn't exist anymore and according to the docs it either
had the same meaning or was implied by -no-user-config so it wouldn't be
needed anyway.  -balloon doesn't exist anymore and according to
https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg06985.html
"-balloon none" was a nop, but I suspect -nodefaults may have already
had the effect of disabling creation of the virtio-balloon device.

tools/test-runner.c

@@ -298,7 +298,6 @@ static char *const qemu_argv[] = {
 	"",
 	"-machine", "type=q35,accel=kvm:tcg",
 	"-nodefaults",
-	"-nodefconfig",
 	"-no-user-config",
 	"-monitor", "none",
 	"-display", "none",
@@ -306,7 +305,6 @@ static char *const qemu_argv[] = {
 	"-nographic",
 	"-vga", "none",
 	"-net", "none",
-	"-balloon", "none",
 	"-no-acpi",
 	"-no-hpet",
 	"-no-reboot",