Remove id field declaration on the base model.
Remove id field declaration on the base model.

In mongoengine this field is declared / assumed automatically and if we declare
it ourselves it breaks things.

punalpatel/st2,lakshmi-kannan/st2,Plexxi/st2,StackStorm/st2,nzlosh/st2,peak6/st2,emedvedev/st2,tonybaloney/st2,punalpatel/st2,tonybaloney/st2,Plexxi/st2,peak6/st2,tonybaloney/st2,punalpatel/st2,nzlosh/st2,pixelrebel/st2,nzlosh/st2,peak6/st2,lakshmi-kannan/st2,pixelrebel/st2,nzlosh/st2,emedvedev/st2,Plexxi/st2,lakshmi-kannan/st2,StackStorm/st2,emedvedev/st2,Plexxi/st2,StackStorm/st2,StackStorm/st2,pixelrebel/st2