Update base APIControllerWithRBACTestCase class - insert default system_admin, admin and observer users with corresponding role assignments.
Update base APIControllerWithRBACTestCase class - insert default system_admin,
admin and observer users with corresponding role assignments.

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