Revert "Arcyd: revert me, combine archive pushes"

This reverts commit 1388d1c1ba41d2aa8d73b652b25df1c7b5a427c2.

Test Plan:
$ ./precommit.sh
$ ./testbed/arcyd/acceptance_tests.sh

exercise abandoned reviews with low threshold in
$ ./testbed/arcyd/test_shell.sh