This patch removes the options_iter function and prepares marconi's code
base to play nice with oslo's config.generator. The replacement of lists
with tuples is necessary to avoid oslo's config.generator to parse the
globally defined options. In Marconi's case, we want it to use the
registered entry_points. (This is a workaround).
Change-Id: I56995fe16cd0b6e092b522dac3c32e4ec75bb269
c3f6e4f79a