CRAS: D-Bus: thread-safety fixes for dbus tests
CRAS: D-Bus: thread-safety fixes for dbus tests

BUG=none
TEST=make check succeeds in loop for a day

Change-Id: Icdeab65cd3da7d33a315a3402547e14a14523553
Signed-off-by: Scott James Remnant <6b88cbe64f92c5d64ffbf57d7b3d2efc0467fe34@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/39346
Reviewed-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>

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