Update get_waiter to use new interface

I've added tests for this function (was previously untested)
to ensure we don't regress on this again in the future.
Update CHANGELOG with bugfix
Call super() in ConfigureCOmmand

Fixes an issue when you try to access the arg_table property,
which was breaking our html doc builds.
Merge branch 'emr-waiter' into develop

* emr-waiter:
  Update CHANGELOG with bugfix
  Update get_waiter to use new interface
Merge branch 'configure-arg-table' into develop

* configure-arg-table:
  Call super() in ConfigureCOmmand
Add retry bugfix to the changelog