Fixed message for cmd /bomb spawnbomb arenaName

mc.euro.demolition.commands.BombExecutor#spawnbomb()

lines 64-80:
No message was being displayed for a successful command execution.
So the user didn't know if the command did anything.

The msg was always there. It just wasn't executing properly... Probably
because of the return statements of the other commands being executed.

Now runs the commands
/aa select arenaName
/aa addspawn
inside an if-statement:
true = success msg
false = failure msg
Added failure msg to spawnbomb()