We need all_collection_ids to be initialized outside the loop that
iterates over all the refs; otherwise it only has the collection IDs
from the last ref (and related).
This fixes a bug where flatpak only includes the ostree-metadata and
appstream data for the collection IDs associated with the last ref given
on the command line and its runtime and related refs. So flatpak now
includes ostree-metadata and appstream data for collection IDs
associated with all the refs given (and their runtimes and related
refs).
Closes: #1930
Approved by: treitter