autotest: WiFiManager: Test GUID in configured service

Test that we can use ConfigureService to create a WiFi
service and connect to it.  Test that after destroying
the service via DeleteEntry, the GUID property of the
service is no longer set.  Test that performing another
ConfigureService with a different passphrase succeeds.

BUG=chromium-os:34004
TEST=Run test with fix for 34004 in it.
CQ-DEPENDS=I2f54adcc4a62c496d1322fa4c3e772620bb74ff8

Change-Id: I399de59501df8ac4ba00e6027727264471c91ee9
Reviewed-on: https://gerrit.chromium.org/gerrit/32947
Reviewed-by: Wade Guthrie <wdg@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
2 files changed