CI failures due to JMX client heartbeat thread

[Bruce Schuchardt]

We have 23 CI failure tickets concerning suspect strings from "JMX 
client heartbeat" threads.  I think we should add this to 
ExpectedStrings.java and close these tickets.  The suspect strings are 
coming from javax.management.remote.rmi.RMIConnector and I don't think 
there's anything we can do about them.  Most, if not all, are assigned 
to security or JMX components.

   GEODE-1858
   GEODE-1955
   GEODE-1492
   GEODE-1539
   GEODE-1538
   GEODE-1773
   GEODE-1922
   GEODE-1482
   GEODE-1475
   GEODE-1480
   GEODE-1481
   GEODE-1826
   GEODE-1825
   GEODE-1820
   GEODE-1878
   GEODE-1879
   GEODE-1877
   GEODE-1875
   GEODE-1876
   GEODE-1499
   GEODE-1476
   GEODE-1869
   GEODE-1769