umpire_docker: move host side shared directory to /shared

Installed of mounting PWD as shared directory in the container, we mount
the host side '/shared' directory instead since PWD may vanish in the
future.

BUG=chromium:499135
TEST=`umpire_docker.sh start` and make sure /shared is mounted in the
container.

Change-Id: I48eba12eb3f7b7bf73d608f1f097a3df991eb7f3
Reviewed-on: https://chromium-review.googlesource.com/276985
Reviewed-by: Hsu Wei-Cheng <mojahsu@chromium.org>
Commit-Queue: Wei-Ning Huang <wnhuang@chromium.org>
Tested-by: Wei-Ning Huang <wnhuang@chromium.org>
1 file changed