Revert "Do not call safe erase on benchmark data."

This reverts commit 17f0261024.

The password can be set by user through expeorted API, we should
not keep traces of derived key from a real password.

lib/crypto_backend/pbkdf_check.c

@@ -299,8 +299,10 @@ static int crypt_argon2_check(const char *kdf, const char *password,
 
 	} while (ms < ms_atleast || ms > ms_atmost);
 out:
-	free(key);
-
+	if (key) {
+		crypt_backend_memzero(key, key_length);
+		free(key);
+	}
 	return r;
 }
 
@@ -378,8 +380,10 @@ static int crypt_pbkdf_check(const char *kdf, const char *hash,
 		}
 	}
 out:
-	free(key);
-
+	if (key) {
+		crypt_backend_memzero(key, key_length);
+		free(key);
+	}
 	return r;
 }