LLAP: fix wrapinputformat for client/server; fix server init to use config

1) Null check right now prevents NPE when split generation tries to wrap input format and IO is not initialized.
There should be a flag visible via interface somewhere that will allow us to check if we are inside the service instead.

2) Server startup disregards the io.enabled config setting. Not clear if it makes sense to run service w/io disabled, need to make it explicit (and remove the setting if not, cause it makes no sense except in q files).