fixes for ProposerAddress

- state.MakeBlock takes a proposerAddr
- validateBlock only checks that the ProposerAddress is in the validator
  set
- fix raceyness from bad proposer test:
  - use privValidator to get the proposer address (instead of racy
    state)
  - note we had to remove the test that checked the correct proposer was
    included for higher rounds because we don't have a good way to test
    this with multiple consensus states and not using the
    privValidator.Address while calling createProposalBlock was a hack!

state/validation_test.go

@@ -72,4 +72,7 @@ func TestValidateBlock(t *testing.T) {
 	block.ProposerAddress = ed25519.GenPrivKey().PubKey().Address()
 	err = blockExec.ValidateBlock(state, block)
 	require.Error(t, err)
+	block.ProposerAddress = []byte("wrong size")
+	err = blockExec.ValidateBlock(state, block)
+	require.Error(t, err)
 }