GEODE-6764: Fix tests broken and flaky on Windows (apache#3577)

- ExportConfigCommandTest was broken by refactorings around removing
  LegacyCommandResult.
- AvailablePortHelperIntegrationTest has always been flaky on Windows.
  By default, Windows uses a bunch more ports than Linux, so some of
  these tests just don't work reliably as larger port ranges are not
  open and available on Windows.

geode-core/src/integrationTest/java/org/apache/geode/internal/AvailablePortHelperIntegrationTest.java

@@ -24,6 +24,7 @@
 import static org.apache.geode.internal.AvailablePortHelper.getRandomAvailableUDPPort;
 import static org.apache.geode.internal.AvailablePortHelper.initializeUniquePortRange;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assume.assumeFalse;
 
 import java.io.IOException;
 import java.net.InetSocketAddress;
@@ -42,6 +43,7 @@
 import org.junit.runner.RunWith;
 
 import org.apache.geode.internal.AvailablePort.Keeper;
+import org.apache.geode.internal.lang.SystemUtils;
 
 @RunWith(JUnitParamsRunner.class)
 public class AvailablePortHelperIntegrationTest {
@@ -266,6 +268,10 @@ public void getRandomAvailableTCPPort_returnsUniqueValues(final boolean useMembe
   @Parameters({"true", "false"})
   public void initializeUniquePortRange_willReturnSamePortsForSameRange(
       final boolean useMembershipPortRange) {
+    assumeFalse(
+        "Windows has ports scattered throughout the range that makes this test difficult to pass consistently",
+        SystemUtils.isWindows());
+
     for (int i = 0; i < 100; ++i) {
       initializeUniquePortRange(i);
       int[] testPorts = getRandomAvailableTCPPorts(3, useMembershipPortRange);
@@ -278,6 +284,10 @@ public void initializeUniquePortRange_willReturnSamePortsForSameRange(
   @Parameters({"true", "false"})
   public void initializeUniquePortRange_willReturnUniquePortsForUniqueRanges(
       final boolean useMembershipPortRange) {
+    assumeFalse(
+        "Windows has ports scattered throughout the range that makes this test difficult to pass consistently",
+        SystemUtils.isWindows());
+
     Set<Integer> ports = new HashSet<>();
 
     for (int i = 0; i < 100; ++i) {

geode-core/src/test/java/org/apache/geode/management/internal/cli/commands/ExportConfigCommandTest.java

@@ -44,6 +44,6 @@ public void before() throws Exception {
   public void incorrectDirectoryShowsError() throws Exception {
     String wrongDir = temp.newFile().getAbsolutePath();
     gfsh.executeAndAssertThat(command, "export config --dir=" + wrongDir).statusIsError()
-        .containsOutput(wrongDir.replace("\\", "\\\\") + " is not a directory");
+        .containsOutput(wrongDir + " is not a directory");
   }
 }