Fixed a typo when computing vbucketlist size for tap messages.

Change-Id: I2e3807f976363e8b8bd985e9b6faa283875ed7f1
Reviewed-on: http://review.couchbase.org/10294
Tested-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>

src/main/java/net/spy/memcached/tapmessage/RequestMessage.java

@@ -104,7 +104,7 @@ public void setBackfill(long date) {
   public void setVbucketlist(short[] vbs) {
     int oldSize = (vblist.length + 1) * 2;
     int newSize = (vbs.length + 1) * 2;
-    totalbody = +newSize - oldSize;
+    totalbody += newSize - oldSize;
     vblist = vbs;
   }