shared/dropin: improve error message

We're not just sorting, but actually creating the list. We can
also use the output parameter directly, without a temporary variable.

src/shared/dropin.c

@@ -187,7 +187,7 @@ int unit_file_find_dropin_paths(
                 Set *names,
                 char ***ret) {
 
-        _cleanup_strv_free_ char **dirs = NULL, **ans = NULL;
+        _cleanup_strv_free_ char **dirs = NULL;
         Iterator i;
         char *t, **p;
         int r;
@@ -203,12 +203,9 @@ int unit_file_find_dropin_paths(
                 return 0;
         }
 
-        r = conf_files_list_strv(&ans, file_suffix, NULL, (const char**) dirs);
+        r = conf_files_list_strv(ret, file_suffix, NULL, (const char**) dirs);
         if (r < 0)
-                return log_warning_errno(r, "Failed to sort the list of configuration files: %m");
-
-        *ret = ans;
-        ans = NULL;
+                return log_warning_errno(r, "Failed to create the list of configuration files: %m");
 
         return 1;
 }