Check block CLI command (#4240)

* Check block operation

* Update client/cli/src/lib.rs

* Update client/cli/src/params.rs

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

@@ -659,6 +659,7 @@ pub mod tests {
 			auxiliary: Vec::new(),
 			fork_choice: ForkChoiceStrategy::LongestChain,
 			allow_missing_state: true,
+			import_existing: false,
 		};
 		do_import_block::<_, _, _, TestJustification>(
 			&client,