923792 - Errata queries during sync don't properly limit returned data

This patch uses the criteria to restrict package metadata snippets from being included with mongo queries.

Sync of RHEL 6.2 to CDN with 4 threads took 70 minutes
and ended up ~1.1GB of memory usage.

apache   14571 75.2 14.6 2504504 1121640 ?     Sl   10:06  55:17  \_ (wsgi:pulp)

Previously we were seeing usage of ~3.5GB