Use signalAll in SynchronizationPoint

to prevent a thread from not being notified about a change of the state
of the SynchronizationPoint.

If two threads are waiting for a change, which could happen e.g. because
of a connectivity change and one thread does instantShutdown() while the
other handles connectionClosedOnError(), then only one thread, usually
the one handling connectionClosedOnError(), would be notified and
resumed.

Fixes SMACK-652.

smack-core/src/main/java/org/jivesoftware/smack/SynchronizationPoint.java

@@ -153,7 +153,7 @@ public class SynchronizationPoint<E extends Exception> {
         connectionLock.lock();
         try {
             state = State.Success;
-            condition.signal();
+            condition.signalAll();
         }
         finally {
             connectionLock.unlock();
@@ -174,7 +174,7 @@ public class SynchronizationPoint<E extends Exception> {
         try {
             state = State.Failure;
             this.failureException = failureException;
-            condition.signal();
+            condition.signalAll();
         }
         finally {
             connectionLock.unlock();