Fix ordering of reported issues
Fix ordering of reported issues

Previously we were passing all the issues through a map and so losing
the order in which they were generated. This change still keeps the
grouping behavior, but emits the messages in the order of their first
occurrence.

Bug: b/150221484

google/agi,google/agi,google/agi,google/agi,google/agi,google/agi,google/agi,google/agi