Kokoro: Rebase changes to ToT before testing
Kokoro: Rebase changes to ToT before testing

By default Kokoro will use changes as they come from gerrit, which may
have an outdated parent. We want to make sure that we are always testing
against tip of tree so we are confident the presubmit test result will
reflect the postsubmit results.

BUG=b:202275156
TEST=Tested in Kokoro

Change-Id: I2a1d2860a361eee741dc522c9859e32890ff15bf
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3229947
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm