Add ProcessBuilderTest#testRedirectInherit() to known failures

This test does fairly low level operations that previously exposed
other kernel issues. So far it has been observed failing 1/10 times
on an Android L kernel but never on CTS. Therefore, adding to list
of known failures. testRedirectErrorStream_outputAndErrorAreMerged
has not yet been observed to fail but is similar; it may need to be
added to the list if it fails in future.

Test: cts-tradefed run cts -c libcore.java.lang.ProcessBuilderTest

Bug: 27464570
Change-Id: I5d67f67099e66cba4d75d9bf621609cd2d88d58a
diff --git a/tools/libcore_failures.txt b/tools/libcore_failures.txt
index 996f2f8..bf8d12b 100644
--- a/tools/libcore_failures.txt
+++ b/tools/libcore_failures.txt
@@ -260,5 +260,12 @@
   bug: 30107038,
   modes: [device],
   names: ["org.apache.harmony.tests.java.lang.ProcessTest#test_destroyForcibly"]
+},
+{
+  description: "Flaky failure, possibly caused by a kernel bug accessing /proc/",
+  result: EXEC_FAILED,
+  bug: 27464570,
+  modes: [device],
+  names: ["libcore.java.lang.ProcessBuilderTest#testRedirectInherit"]
 }
 ]