Add changelog entry for the workflow service error handling fix
Add changelog entry for the workflow service error handling fix

Add changelog entry for the workflow service fix to handle unexpected coordinator and database errors.

nzlosh/st2,Plexxi/st2,nzlosh/st2,Plexxi/st2,Plexxi/st2,nzlosh/st2,nzlosh/st2,StackStorm/st2,StackStorm/st2,StackStorm/st2,Plexxi/st2,StackStorm/st2