Sync skywalking upstream version and reduce Cassandra storage size (#… #51

Job	Run time
test	16m 19s
test_docker (receiver-zipkin-activemq)	6m 21s
test_docker (receiver-zipkin-http)	6m 14s
test_docker (receiver-zipkin-kafka)	6m 23s
test_docker (receiver-zipkin-rabbitmq)	6m 21s
test_docker (receiver-zipkin-scribe)	5m 28s
test_docker (receiver-zipkin-grpc)	6m 3s
test_docker (storage-cassandra)	6m 21s
	59m 30s

Provide feedback