On diskless SN, the nodes file of goconserver is missing when
reinstalling. This patch add a column in nodehm table to help
recover the console information on service node.
```
[root@c910f03c09k04 ~]# makegocons -q
NODE SERVER STATE
c910f03c09k05 c910f03c09k04.pok.stglabs.ibm.com error
node-7912ac1-06vag36 c910f03c09k04.pok.stglabs.ibm.com error
NODE SERVER STATE
c910f03c09k04 c910f03c09k03.pok.stglabs.ibm.com connected
[root@c910f03c09k04 ~]# rm /var/lib/goconserver/*
rm: remove regular file ‘/var/lib/goconserver/nodes.json’? y
rm: remove regular file ‘/var/lib/goconserver/nodes.json.bak’? y
[root@c910f03c09k04 ~]# service xcatd restart
Restarting xcatd (via systemctl): [ OK ]
[root@c910f03c09k04 ~]# makegocons -q
NODE SERVER STATE
c910f03c09k05 c910f03c09k04.pok.stglabs.ibm.com error
node-7912ac1-06vag36 c910f03c09k04.pok.stglabs.ibm.com error
NODE SERVER STATE
c910f03c09k04 c910f03c09k03.pok.stglabs.ibm.com connected
```