JAVA-674: Fixed exception messaging for number of concurrent requests allowed

Author: jyemin

src/main/com/mongodb/DBPortPool.java

@@ -208,7 +208,7 @@ protected int pick( int recommended, boolean couldCreate ){
     public DBPort get() {
         DBPort port = null;
         if ( ! _waitingSem.tryAcquire() )
-            throw new SemaphoresOut(_waitingSem.availablePermits() );
+            throw new SemaphoresOut(_options.connectionsPerHost * _options.threadsAllowedToBlockForConnectionMultiplier);
 
         try {
             port = get( _options.maxWaitTime );