bump version to v2.8.1
bump version to v2.8.1

(cherry picked from commit a80231648a1473929271764b920a8e346f6de844)

adamreese/deployment-manager,jascott1/helm,technosophos/deployment-manager,adamreese/deployment-manager,technosophos/deployment-manager,technosophos/deployment-manager,appscode/helm,adamreese/deployment-manager,michelleN/deployment-manager,helm/helm,technosophos/deployment-manager,eicnix/helm,SlickNik/helm,adamreese/deployment-manager,jascott1/helm,adamreese/deployment-manager,michelleN/deployment-manager,technosophos/k8s-helm,fibonacci1729/helm,adamreese/helm,technosophos/k8s-helm,technosophos/deployment-manager,SlickNik/helm,appscode/helm,helm/helm,adamreese/helm,michelleN/deployment-manager,bacongobbler/helm,bacongobbler/helm,eicnix/helm,fibonacci1729/helm,michelleN/deployment-manager