addModule should not be alowed on single-server installs

mcsadmin addModule command should error out with msg that its not allowed due to being a single-server install

mcsadmin> starts
startsystem Fri Mar 17 16:22:09 2017
startSystem command, 'columnstore' service is down, sending command to
start the 'columnstore' service on all modules

System being started, please wait.................
Successful start of System

mcsadmin> getsystemn
getsystemnetworkconfig Fri Mar 17 16:23:23 2017

System Network Configuration

Module Name Module Description NIC ID Host Name IP Address
----------- ------------------------- ------ --------- ---------------
pm1 Performance Module #1 1 localhost 127.0.0.1

mcsadmin> addmodule pm2 pm2 Calpont1
addmodule Fri Mar 17 16:23:27 2017
IP Address of pm2 not found, enter IP Address or enter 'abort'
Please enter: