Catch any unexpected exceptions while closing a replication

If the replication only partially initialized and then threw an
exception, we may find that the underlying JSch connection is only
partially initialized.  Calling tn.close() from our finally block
may throw a NullPointerException from within JSch, as JSch tries
to cleanup uninitialized resources.

By wrapping our close call in a try/catch we can ensure that any
close failure is logged and then ignored, so that if the close was
execting becaues an exception was thrown that the original exception
can propagate to our exception handle and also be logged.

Signed-off-by: Shawn O. Pearce <sop@google.com>

src/main/java/com/google/gerrit/git/PushQueue.java

@@ -158,7 +158,11 @@ public class PushQueue {
       log.error("Cannot replicate to " + op.uri, e);
       return;
     } finally {
-      tn.close();
+      try {
+        tn.close();
+      } catch (Throwable e2){
+        log.warn("Unexpected error while closing " + op.uri, e2);
+      }
     }
 
     for (final RemoteRefUpdate u : res.getRemoteUpdates()) {