Fix data path to qemu in CrOS generate_vm_runner_script gn target.

It changed from -r2 to -r3 recently, so the path is no longer valid.

This just lists the parent dir instead. (qemu should be the only thing
in it).

Bug: 828607
Change-Id: I2bc72b8f4202fedadc5274031d395df72ddd4276
Reviewed-on: https://chromium-review.googlesource.com/1014489Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#551164}

build/config/chromeos/rules.gni

@@ -9,7 +9,7 @@ template("generate_vm_runner_script") {
   _cros_sdk = getenv("SDK_VERSION")
 
   _vm_image_path = "//build/cros_cache/chrome-sdk/tarballs/${_cros_board}+${_cros_sdk}+chromiumos_qemu_image.tar.xz/chromiumos_qemu_image.bin"
-  _qemu_dir = "//build/cros_cache/chrome-sdk/tarballs/${_cros_board}+${_cros_sdk}+app-emulation/qemu-2.6.0-r2.tbz2/"
+  _qemu_dir = "//build/cros_cache/chrome-sdk/tarballs/${_cros_board}+${_cros_sdk}+app-emulation/"
 
   action(target_name) {
     forward_variables_from(invoker, [ "testonly" ])