Update Dockerfile and streamline build steps #2269

Job	Run time
build-all	3m 8s
tests (scylla, -Pscylla-murmur -Dtest="*/hadoop/", murmur-hadoop, -Pjava-11, 11)	11m 26s
tests (scylla, -Pscylla-murmur -Dtest="*/diskstorage/cql/", murmur-diskstorage-java8, 8)	14m 44s
tests (scylla, -Pscylla-murmur -Dtest="*/core/cql/", murmur-core-java8, 8)	4m 14s
tests (scylla, -Pscylla-murmur -Dtest="*/diskstorage/cql/", murmur-diskstorage, -Pjava-11, 11)	15m 2s
tests (scylla, -Pscylla-murmur -Dtest="*/graphdb/cql/", murmur-graphdb-java8, 8)	57m 3s
tests (scylla, -Pscylla-murmur -Dtest="*/graphdb/cql/", murmur-graphdb, -Pjava-11, 11)	57m 7s
tests (scylla, -Pscylla-murmur -Dtest="*/core/cql/", murmur-core, -Pjava-11, 11)	4m 8s
tests (scylla, -Pscylla-murmur -Dtest="*/hadoop/", murmur-hadoop-java8, 8)	11m 47s
	2h 58m 39s

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