use gauge for  metrics reported by containers and one small bugfix
use gauge for clusterwide metrics
Merge branch 'release/2.6.0' of github.com:caskdata/cdap into feature/fix_resourcereport_metrics

Conflicts:
	cdap-app-fabric/src/main/java/co/cask/cdap/internal/app/runtime/distributed/DistributedProgramRuntimeService.java
Merge pull request #802 from caskdata/feature/fix_resourcereport_metrics

Feature/fix resourcereport metrics