shill: wifi: remove automatic transition out of failure

It turns out that the automatic transition is not necessary.
Furthermore, it actually confuses Chrome. With the automatic
transition, Chrome will not show the error mole for a (suspected)
bad WPA password.

Note that this commit fixes a bug in the SuspectCredentialsYieldFailure
unit test, in that the test used to rely on the internal state of
a MockService object, even though the method that updated that state
was mocked out.

BUG=chromium-os:21844
TEST=manual (see below), unit tests

Manual testing:
 1. boot device
 2. attempt connection to a fresh (never before used on the device) WPA SSID,
    with the wrong password
 3. observe that the "Join Wi-Fi network" dialog is shown again, with
    "Incorrect password" in red, below the password box
 4. hit "Cancel"

 5. log in
 6. attempt connection to another fresh WPA SSID (not the same as in step 2),
    with an incorrect password
 7. observe that the "Join Wi-Fi network" dialog is shown again, with
    "Incorrect password" in red, below the password box
 8. observe "Network Connection Error" mole, with text "Failed to connect to
    network <SSID>: Bad passphrase"
 9. hit "Cancel"
10. log out

11. ctrl-alt-f2
12. login as root
13. pkill -9 chrome && \
    rm -rf /home/chronos/Local\ State /home/chronos/.oobe_completed && \
    sudo reboot
14. attempt connection to another fresh WPA SSID (not the same as in step 2
    or step 6), with an incorrect password
15. observe "Network Connection Error" mole, with text "Failed to connect to
    network <SSID>: Bad passphrase"
16. enter correct password
17. observe successful connection

Change-Id: I97c6f6b3473a66b6e691aa0b400a131f32ebf3c0
Reviewed-on: https://gerrit.chromium.org/gerrit/28547
Tested-by: mukesh agrawal <quiche@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: mukesh agrawal <quiche@chromium.org>
diff --git a/mock_wifi_service.h b/mock_wifi_service.h
index c35475b..9468245 100644
--- a/mock_wifi_service.h
+++ b/mock_wifi_service.h
@@ -28,6 +28,7 @@
   virtual ~MockWiFiService();
 
   MOCK_METHOD1(SetFailure, void(ConnectFailure failure));
+  MOCK_METHOD1(SetFailureSilent, void(ConnectFailure failure));
   MOCK_METHOD1(SetState, void(ConnectState state));
   MOCK_METHOD2(AddEAPCertification, bool(const std::string &name,
                                          size_t depth));