Skips all records that have no 997s or 998s (#1194).

[bwatson78]

• app/models/oai_validation/no_holding_records_rule.rb: creates a new rule excluding any records without either 997s or 998s.
• app/models/oai_validation/rule.rb: inserts new rule into main rule list.
• spec/fixtures/* : creates new 997 fields for records that have neither 997s or 998s.
• spec/models/marc_indexing_spec.rb: removes logic that depended on bringing in fields with neither mentioned fields present.

Backend processing, no screenshots necessary.

[bwatson78]

@abelemlih 65ccf04 addresses the new spec that makes sure these records are skipped.