allow ROOK_API_SERVER_ENDPOINT to be set by user
toolbox: default to rook-api dns name when no k8s service env vars are
given
Added dnsPolicy to rook-tools (K8s required version >1.6)
RBD image support fixes, ensure /etc/ceph is created in toolbox image, return output string in exec even for errors because the ceph tools return useful information there upon error