Add ConnectivityConstraintTest to known failures

ConnectivityConstraintTest was inadvertently removed from the
blacklist in commit 015a287beb01 ("resolved conflicts for merge of
362fdcb7 to master").  It's still broken, so add it back.

Bug: 18117279
Change-Id: Icfab870c7c449a05829646c4179f4a13da588fc4
diff --git a/tests/expectations/knownfailures.txt b/tests/expectations/knownfailures.txt
index 40f4b42..0352154 100644
--- a/tests/expectations/knownfailures.txt
+++ b/tests/expectations/knownfailures.txt
@@ -7,6 +7,13 @@
   bug: 17536113
 },
 {
+  description: "the ConnectivityConstraintTest are not yet stable",
+  names: [
+    "android.jobscheduler.cts.ConnectivityConstraintTest"
+  ],
+  bug: 18117279
+},
+{
   description: "tests a fragile by nature as they rely on hardcoded behavior",
   names: [
     "android.accessibilityservice.cts.AccessibilityTextTraversalTest#testActionNextAndPreviousAtGranularityPageOverText",