win32: Set registry value with SetValueEx not SetValue

_winreg.SetValue only allows to set the default value on a subkey
SetValueEx lets one specify the value name and the value itself.

Additionally as a security measure we're now encapsulating all
exceptions coming from SAS handling to still at least attempt the
login, even if the SAS portion may fail.
This is just a precaution to prevent SSO from breaking due to some
unforeseen bug.

Change-Id: I51d70381de43d62e96f9f24de60bdf0226e20f54
Bug-Url: https://bugzilla.redhat.com/1158470
Signed-off-by: Vinzenz Feenstra <vfeenstr@redhat.com>