fix dashboard report - converting unicode to string

I just used __blah since all other amon private method is using __blah. 
apmon is still used use by DashboardReporter (Actually that seems the only call it is used) Is there any replacement method?

https://github.com/dmwm/WMCore/blob/master/src/python/WMCore/Services/Dashboard/DashboardReporter.py#L13
https://github.com/dmwm/WMCore/blob/master/src/python/WMCore/Services/Dashboard/DashboardReporter.py#L87
...
https://github.com/dmwm/WMCore/blob/master/src/python/WMCore/Services/Dashboard/DashboardAPI.py#L58