run-qemu-robot-test: Use --rm for docker run

When the test runs boot-qemu-test.exp with docker, it does not use --rm
so the container remains after the test exits.

Add --rm so that the container is removed automatically.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: Ie9748bf5fe029c26cd4ec2ca931b44169906bef4
diff --git a/run-qemu-robot-test.sh b/run-qemu-robot-test.sh
index f3e0732..0857c6d 100755
--- a/run-qemu-robot-test.sh
+++ b/run-qemu-robot-test.sh
@@ -107,6 +107,7 @@
   # Start QEMU docker instance
   # root in docker required to open up the https/ssh ports
   obmc_qemu_docker=$(docker run --detach \
+                                --rm \
                                 --user root \
                                 --env HOME=${OBMC_BUILD_DIR} \
                                 --env QEMU_RUN_TIMER=${QEMU_RUN_TIMER} \