Respect .gitignore when cleaning checkout

dup_it_worker was blowing away the output logs folder because we asked
it to ignore the .gitignore rules.

BUG=chromium:724619
TEST=None

Change-Id: I0a610b1403d753f7282618191b2d38c28fa33feb
Reviewed-on: https://chromium-review.googlesource.com/518984
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/bin/dup_it_worker.sh b/bin/dup_it_worker.sh
index 03104b8..4e5cd08 100755
--- a/bin/dup_it_worker.sh
+++ b/bin/dup_it_worker.sh
@@ -37,7 +37,7 @@
 (date && \
  git fetch -q origin && \
  git checkout -qf --detach origin/master && \
- git clean -qfxd && \
+ git clean -qfd && \
  ${DUP_IT_SCRIPT} -s "${dup_it_url}" -p "${dup_it_passwd}" && \
  date) >> "${LOG_FILE}" 2>&1