Ignore GZIPOutputStreamTest failures with concurrent collector.

This test sometimes fail with a
java.util.concurrent.TimeoutException on ART Builbot's
x86-64 concurrent collector configuration:
* libcore.java.util.zip.GZIPOutputStreamTest#testSyncFlushEnabled

Disable it while we investigate.

Bug: 26507762
Change-Id: I12db20be14dfce8f6f668207bc91d57c2cb24c9f
diff --git a/tools/libcore_failures_concurrent_collector.txt b/tools/libcore_failures_concurrent_collector.txt
index 3d25d5f..2cb2c50 100644
--- a/tools/libcore_failures_concurrent_collector.txt
+++ b/tools/libcore_failures_concurrent_collector.txt
@@ -24,10 +24,12 @@
   bug: 26155567
 },
 {
-  description: "TimeoutException on host-x86-concurrent-collector",
+  description: "TimeoutException on host-{x86,x86-64}-concurrent-collector",
   result: EXEC_FAILED,
-  names: ["libcore.java.util.zip.ZipFileTest#testZipFileWithLotsOfEntries,
-           libcore.java.util.zip.ZipInputStreamTest#testLongMessage"],
+  modes: [host],
+  names: ["libcore.java.util.zip.GZIPOutputStreamTest#testSyncFlushEnabled",
+          "libcore.java.util.zip.ZipFileTest#testZipFileWithLotsOfEntries",
+          "libcore.java.util.zip.ZipInputStreamTest#testLongMessage"],
   bug: 26507762
 }
 ]