FilteredServerView
filter out segment callbacks not related to given filter
filtered batch inventory view tests
update realtime tasks to use FilteredServerView
make it explicit it's a concurrent map
require default predicate in ServerInventoryViews
Merge pull request #571 from metamx/filtered-serverview

FiltereServerView
prepare for next release
[maven-release-plugin] prepare release druid-0.6.115
[maven-release-plugin] prepare for next development iteration