fixes ZEN-8150: (reviewed by jhanson, changeset 75967) updateTagSeverityFromDocument was not retreiving severities when called with an empty filter.
Merge pull request #4 from zenoss/feature/ZEN-8152

fixes ZEN-8152: (reviewed by jhanson, changeset 75967) updateTagSeverity...
Merge branch 'develop' of https://github.com/zenoss/zenoss-zep into develop