title: MongoDB C# driver: waiting for replication timed out
body: <p>I use MongoDB 3.0.3 and the C# driver 1.10.0.62.<br>
  I have 2 shards and set the <code>writeConcern: W = 2, WTimeout = 5000</code><br>
  When I use the method <code>col.Insert(data, writeConcern)</code> the program always throw exceptions as below:<br>
  <code>MongoDB.Driver.MongoWriteConcernException: WriteConcern detected an error 'waiting for replication timed out at shard01'. (Response was { "ok" : 1, "code" : 64, "err" : "waiting for replication timed out at shard01", "n" : NumberLong(0) }).</code><br>
  These exceptions occurs frequently. Does anyone know how to handle them??</p>