blockchain: fix bitflipping test with quantized block rewards

Block reward may now be less than the full amount allowed.
This was breaking the bitflipping test.
We now keep track of whether a block which was accepted by the core
has a lower than allowed block reward, and allow this in the test.

src/cryptonote_core/verification_context.h

@@ -48,5 +48,6 @@ namespace cryptonote
     bool m_verifivation_failed; //bad block, should drop connection
     bool m_marked_as_orphaned;
     bool m_already_exists;
+    bool m_partial_block_reward;
   };
 }