Fix exit status of ART script tools/teardown-buildbot-device.sh.

Simplify the logic deleting property_context files from the
chroot and prevent it from making the script return a non-zero
exit status.

Test: sh -x art/tools/teardown-buildbot-device.sh; echo $?
Bug: 34729697
Change-Id: Ia9f34eda2c167b26a6396937c7c4ecec01c86718
diff --git a/tools/teardown-buildbot-device.sh b/tools/teardown-buildbot-device.sh
index df239a2..be2cb27 100755
--- a/tools/teardown-buildbot-device.sh
+++ b/tools/teardown-buildbot-device.sh
@@ -65,6 +65,6 @@
     /plat_property_contexts \
     /nonplat_property_contexts"
   for f in $property_context_files; do
-    adb shell test -f "$f" "&&" rm -f "$ART_TEST_CHROOT$f"
+    adb shell rm -f "$ART_TEST_CHROOT$f"
   done
 fi