fix off by one in setup_height (#988)

chain/src/store.rs

@@ -236,7 +236,7 @@ impl ChainStore for ChainKVStore {
 	fn setup_height(&self, header: &BlockHeader, old_tip: &Tip) -> Result<(), Error> {
 		// remove headers ahead if we backtracked
 		for n in header.height..old_tip.height {
-			self.delete_header_by_height(n)?;
+			self.delete_header_by_height(n + 1)?;
 		}
 		self.build_by_height_index(header, false)
 	}