grandpa: fix creation of justification with equivocating precommits in commit (#11302)

* grandpa: fix creation of justification ancestry

we would reject commits that have precommits targeting blocks lower than the
commit target. when there is an equivocation (or if it the commit is not
minimal) it is possible to have such precommits and we should assume that they
are the round base.

* grandpa: bump to 0.16.0

* grandpa: add test for justification with equivocation

* grandpa: fix failing test

substrate/client/finality-grandpa/src/finality_proof.rs

@@ -237,7 +237,7 @@ where
 }
 
 #[cfg(test)]
-pub(crate) mod tests {
+mod tests {
 	use super::*;
 	use crate::{authorities::AuthoritySetChanges, BlockNumberOps, ClientError, SetId};
 	use futures::executor::block_on;
@@ -271,6 +271,7 @@ pub(crate) mod tests {
 		let justification: GrandpaJustification<Block> =
 			Decode::decode(&mut &proof.justification[..])
 				.map_err(|_| ClientError::JustificationDecode)?;
+
 		justification.verify(current_set_id, &current_authorities)?;
 
 		Ok(proof)
@@ -370,7 +371,7 @@ pub(crate) mod tests {
 
 	#[test]
 	fn finality_proof_check_fails_with_incomplete_justification() {
-		let (client, _, blocks) = test_blockchain(8, &[4, 5, 8]);
+		let (_, _, blocks) = test_blockchain(8, &[4, 5, 8]);
 
 		// Create a commit without precommits
 		let commit = finality_grandpa::Commit {
@@ -378,7 +379,9 @@ pub(crate) mod tests {
 			target_number: *blocks[7].header().number(),
 			precommits: Vec::new(),
 		};
-		let grandpa_just = GrandpaJustification::from_commit(&client, 8, commit).unwrap();
+
+		let grandpa_just =
+			GrandpaJustification::<Block> { round: 8, votes_ancestries: Vec::new(), commit };
 
 		let finality_proof = FinalityProof {
 			block: header(2).hash(),