fixes spurious exception in tests

[keith-turner]

Seeing exceptions like the following when running ITs. This exception does not cause the test to fail, it is just printed after the test runs. The reason it happens is the code ServerKeywordExecutable.getConfiguration() is run w/o the java system property for accumulo.properties set. So it searches and finds test/src/main/resources/accumulo.properties on the classpath which does not contain instance.volumes. This fix sets the java system property so that accumulo.properties created by mini is found. Opening this as draft for the moment because I am not sure if this is the best way to fix this (feels a bit hacky).

java.lang.IllegalArgumentException: Missing required property instance.volumes
	at org.apache.accumulo.core.volume.VolumeConfiguration.getVolumeUris(VolumeConfiguration.java:41)
	at org.apache.accumulo.server.fs.VolumeManagerImpl.get(VolumeManagerImpl.java:435)
	at org.apache.accumulo.server.ServerInfo.lambda$new$10(ServerInfo.java:132)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.server.ServerInfo.getVolumeManager(ServerInfo.java:156)
	at org.apache.accumulo.server.ServerInfo.lambda$fromServerConfig$3(ServerInfo.java:66)
	at org.apache.accumulo.server.ServerInfo.lambda$new$16(ServerInfo.java:147)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.server.ServerInfo.getInstanceId(ServerInfo.java:161)
	at org.apache.accumulo.server.ServerInfo.lambda$new$12(ServerInfo.java:139)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.server.ServerInfo.getCredentials(ServerInfo.java:212)
	at org.apache.accumulo.server.ServerInfo.getPrincipal(ServerInfo.java:181)
	at org.apache.accumulo.core.clientImpl.ClientContext.lambda$new$1(ClientContext.java:263)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.core.clientImpl.ClientContext.getZooSession(ClientContext.java:1160)
	at org.apache.accumulo.server.ServerContext.lambda$new$0(ServerContext.java:138)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.server.ServerContext.getPropStore(ServerContext.java:463)
	at org.apache.accumulo.server.conf.ZooBasedConfiguration.<init>(ZooBasedConfiguration.java:63)
	at org.apache.accumulo.server.conf.SystemConfiguration.<init>(SystemConfiguration.java:36)
	at org.apache.accumulo.server.conf.ServerConfigurationFactory.lambda$new$0(ServerConfigurationFactory.java:87)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.server.conf.ServerConfigurationFactory.getSystemConfiguration(ServerConfigurationFactory.java:126)
	at org.apache.accumulo.server.conf.ServerConfigurationFactory.lambda$new$1(ServerConfigurationFactory.java:93)
	at com.google.common.base.Suppliers$NonSerializableMemoizingSupplier.get(Suppliers.java:198)
	at org.apache.accumulo.server.conf.ServerConfigurationFactory.getResourceGroupConfiguration(ServerConfigurationFactory.java:121)
	at org.apache.accumulo.server.ServerContext.getConfiguration(ServerContext.java:194)
	at org.apache.accumulo.server.util.ServerKeywordExecutable.doExecute(ServerKeywordExecutable.java:56)
	at org.apache.accumulo.server.util.ServerKeywordExecutable.doExecute(ServerKeywordExecutable.java:31)
	at org.apache.accumulo.core.cli.BaseKeywordExecutable.execute(BaseKeywordExecutable.java:50)
	at org.apache.accumulo.miniclusterImpl.MiniAccumuloClusterControl.stop(MiniAccumuloClusterControl.java:318)
	at org.apache.accumulo.miniclusterImpl.MiniAccumuloClusterImpl.stop(MiniAccumuloClusterImpl.java:1021)
	at org.apache.accumulo.harness.AccumuloClusterHarness.teardownCluster(AccumuloClusterHarness.java:207)

[dlmarion]

I did this same fix in some of the ITs that I was working on recently, and I was wondering if we were going to have to move this up into some higher level code. May want to remove the references to SiteConfiguration.ACCUMULO_PROPERTIES_PROPERTY in the other ITs to see if they still pass.