SecureTestCluster should allow its subclasses to pass their Class reference on HBaseKerberosUtils.setSSLConfiguration

Was working on a third party project that relies on hbase-server as a dependency and defines a UT class that extends SecureTestCluster. In this project, hbase-server jar is added on the test classpath, and it relies on KeyStoreTestUtil to decide where to place related ssl files. Current KeyStoreTestUtil code assumes related class files would be under an existing local FS path, but when those are loaded from a jar, related class URI path returns null and causes an NPE that errors out the test execution. 

The test code in this case extends SecureTestCluster, so when SecureTestCluster.setup runs, it calls HBaseKerberosUtils.setSSLConfiguration passing its own class reference here.
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HBaseKerberosUtils.setSSLConfiguration, in turn, calls KeyStoreTestUtil.getClasspathDir here. KeyStoreTestUtil.getClasspathDir uses the passed class reference name to look for its related resource in the class loader. This line returns an URL value as follows, when the passed class reference resource resides on jar file in the class loader (instead of being in a valid local FS path):

jar:file:/Users/wellingtonchevreuil/.m2/repository/org/apache/hbase/hbase-server/2.2.3./hbase-server-2.2.3-tests.jar!/org/apache/hadoop/hbase/security/token/SecureTestCluster.class

This causes subsequent line calling url.toURI().getPath() to return null, then we get the NPE thrown in the following line, and the test errors out:

java.lang.NullPointerException at org.apache.hadoop.hbase.http.ssl.KeyStoreTestUtil.getClasspathDir(KeyStoreTestUtil.java:59) at org.apache.hadoop.hbase.security.HBaseKerberosUtils.setSSLConfiguration(HBaseKerberosUtils.java:173) at org.apache.hadoop.hbase.security.token.SecureTestCluster.setUp(SecureTestCluster.java:74) at com.cloudera.hbase.security.token.TestCldrManualDelegationToken.setUp(TestCldrManualDelegationToken.java:168) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27) at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:298) at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:292) at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266) at java.util.concurrent.FutureTask.run(FutureTask.java) at java.lang.Thread.run(Thread.java:748