signer: fix golint errors (#16653)

* signer/*: golint fixes

Specifically naming and comment formatting for documentation

* signer/*: fixed naming error crashing build

* signer/*: corrected error

* signer/core: fix tiny error whitespace

* signer/rules: fix test refactor

signer/storage/aes_gcm_storage.go

@@ -14,6 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
 //
+
 package storage
 
 import (
@@ -106,10 +107,8 @@ func (s *AESEncryptedStorage) readEncryptedStorage() (map[string]storedCredentia
 		if os.IsNotExist(err) {
 			// Doesn't exist yet
 			return creds, nil
-
-		} else {
-			log.Warn("Failed to read encrypted storage", "err", err, "file", s.filename)
 		}
+		log.Warn("Failed to read encrypted storage", "err", err, "file", s.filename)
 	}
 	if err = json.Unmarshal(raw, &creds); err != nil {
 		log.Warn("Failed to unmarshal encrypted storage", "err", err, "file", s.filename)