Arcyd: refactor, remove unused repooptions

We haven't needed the 'options stored in a ref' functionality for some
time, simplify things by removing it all.

Test Plan:
$ ./precommit.sh
$ git grep repooptions

exercise the multiple admin email path
$ ./testbed/arcyd/test_shell.sh
    $ exit
Arcyd: refactor, inline '_do'

The wrapper function 'do' is now trivial, inline the '_do' function.

Move the implementation detail '_flatten_list' to the bottom of the
file.

Test Plan:
$ ./precommit.sh