Reset Signin state both before and after signin tests.

Reset Signin state both before and after signin tests.

We assume a account id <-> name mapping is available for accounts in the
token service as well as for the signed in account.

This will eliminate some illegal signin states after running the tests.

BUG=542962, 535211
Committed: https://crrev.com/d966e6f1df247a39ddafab5f80956bf464c9b1a3
Cr-Commit-Position: refs/heads/master@{#354511}

[knn, 2015-10-16 12:12:41]

knn@chromium.org changed reviewers:
+ nyquist@chromium.org

[knn, 2015-10-16 12:12:42]

PTAL. Thanks!

[nyquist, 2015-10-16 13:50:35]

lgtm

[knn, 2015-10-16 13:51:04]

The CQ bit was checked by knn@chromium.org

[commit-bot: I haz the power, 2015-10-16 13:51:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1409083002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1409083002/1

[commit-bot: I haz the power, 2015-10-16 14:07:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-16 14:08:26]

Patchset 1 (id:??) landed as
https://crrev.com/d966e6f1df247a39ddafab5f80956bf464c9b1a3
Cr-Commit-Position: refs/heads/master@{#354511}