QPID-5982: [Java Broker] BDB HA: Reset replication transaction id when contact with remote node is lost

* Change BDB HA VHN tab so that replication transaction id -1 is shown as N/A
* Adjust width of VH table on Broker tab to avoid state UNAVAIABLE wrapping over two lines.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1617159 13f79535-47bb-0310-9956-ffa450edef68