Jortel nodes manifest

The PR was originally intended to address both performance and functional issues related to the size of published manifest files.  The primary changes:
- Rename the units.json -> manifest.json
- The manifest now contains:
  - Total number of published units.
  - A list of files containing json encoded lists of units (much like yum repomd files).
- Total units are written to units.json files in batches of 1000.

During performance testing, the follow other issues needed to be addressed and are included in this PR:
- Consumer content unit install, update, and uninstall agent timeouts needed to be increased.  Looking back, they were needlessly too short.
- The publish report was exceeding the max document size in  mongo.  It http nodes distributor report contained more details then were useful.
- Was using downloader default max concurrency.  Adjusted based on testing using the entire RHEL 7 repository.