Network hardware address retrieval is now checked

In some Java security manager configurations, getting hardware address could fail during machine ID definition:

```
java.net.SocketException: No such device
	at reactivemongo.bson.BSONObjectID$.<init>(types.scala:337)
 	at scala.collection.AbstractIterator.find(Iterator.scala:1157)
 	at reactivemongo.bson.BSONObjectID$.<clinit>(types.scala)
 	at scala.collection.Iterator$class.find(Iterator.scala:780)
	at reactivemongo.bson.BSONObjectID$$anonfun$1.apply(types.scala:337)
 	at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
 	at reactivemongo.bson.BSONObjectID$$anonfun$1.apply(types.scala:337)
```

A try / catch has been added to the hardware address access.