Fix HADOOP-100.  Be more consistent about synchronization of access to taskTracker collection.  Contributed by Owen O'Malley.
Fix HADOOP-100.  Be more consistent about synchronization of access to taskTracker collection.  Contributed by Owen O'Malley.

git-svn-id: 4d48d1092ee340c9ada5711cdbe4355b138bc22b@390287 13f79535-47bb-0310-9956-ffa450edef68

awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop,awylie/hadoop