SQL: Ignore environment in CliFixture

If the currenct environment contains `JAVA_TOOLS` then the cli tests
will fail because they do not expect the notification about `JAVA_TOOLS`
that java prints to stdout. The clears the environment before starting
the CLI subprocess in an effort to remove the unexpected output.

Original commit: elastic/x-pack-elasticsearch@5729c1c09b

test/sql-cli-fixture/src/main/java/org/elasticsearch/xpack/sql/cli/fixture/CliFixture.java

@@ -102,6 +102,8 @@ public class CliFixture {
                     command.add(cliJar.toString());
                     command.addAll(Arrays.asList(line.split(" ")));
                     ProcessBuilder cliBuilder = new ProcessBuilder(command);
+                    // Clear the environment to drop JAVA_TOOLS which prints strange things on startup
+                    cliBuilder.environment().clear();
                     cliBuilder.redirectErrorStream(true);
                     Process process = cliBuilder.start();
                     println("started " + command);