Refactor tests for clarity and maintainability #5609

Job	Run time
build-all	3m 26s
tests (hbase, -Pjava-11, -Dtest="*/hadoop/", hbase2-hadoop, 11)	35m 48s
tests (hbase, -Dtest="*/graphdb/hbase/", hbase2-graphdb-java8, 8)	55m 45s
tests (hbase, -Pjava-11, -Dtest="*/diskstorage/hbase/", hbase2-diskstorage, 11)	46m 10s
tests (hbase, -Pjava-11, -Dtest="*/graphdb/hbase/", hbase2-graphdb, 11)	54m 18s
tests (hbase, -Dtest="*/hadoop/", hbase2-hadoop-java8, 8)	29m 26s
tests (hbase, -Dtest="*/diskstorage/hbase/", hbase2-diskstorage-java8, 8)	40m 30s
	4h 25m 23s

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