Fix clippy warnings (#1385)

## Issue Addressed

NA

## Proposed Changes

Fixes most clippy warnings and ignores the rest of them, see issue #1388.

account_manager/src/validator/deposit.rs

@@ -1,6 +1,5 @@
 use crate::VALIDATOR_DIR_FLAG;
 use clap::{App, Arg, ArgMatches};
-use clap_utils;
 use deposit_contract::DEPOSIT_GAS;
 use environment::Environment;
 use futures::compat::Future01CompatExt;

account_manager/src/validator/mod.rs

@@ -28,11 +28,9 @@ pub fn cli_run<T: EthSpec>(matches: &ArgMatches, env: Environment<T>) -> Result<
     match matches.subcommand() {
         (create::CMD, Some(matches)) => create::cli_run::<T>(matches, env, base_wallet_dir),
         (deposit::CMD, Some(matches)) => deposit::cli_run::<T>(matches, env),
-        (unknown, _) => {
-            return Err(format!(
-                "{} does not have a {} command. See --help",
-                CMD, unknown
-            ));
-        }
+        (unknown, _) => Err(format!(
+            "{} does not have a {} command. See --help",
+            CMD, unknown
+        )),
     }
 }