Fix getblock older hex behaviour

[prasannavl]

Summary

• getblock RPC #2291 broke older behaviour of include_hex by properly carrying that across the call tree.
• However this breaks many tests and compatibility. This restores the older behaviour unless version > 2.

Implications

• Storage

  • Database reindex required
  • Database reindex optional
  • Database reindex not required
  • None

• Consensus

  • Network upgrade required
  • Includes backward compatible changes
  • Includes consensus workarounds
  • Includes consensus refactors
  • None