os-util: do not use 'r' for storing loop status

The variable 'r' is usually used for storing return value of functional
call. Let's introduce another boolean to store the current loop status.

No functional change, just refactoring.

src/basic/os-util.c

@@ -149,6 +149,7 @@ int open_extension_release(
 
         _cleanup_close_ int fd = -EBADF;
         _cleanup_free_ char *q = NULL;
+        bool found = false;
         int r;
 
         assert(!extension || (image_class >= 0 && image_class < _IMAGE_CLASS_MAX));
@@ -183,7 +184,6 @@ int open_extension_release(
         if (r < 0)
                 return log_debug_errno(r, "Cannot open %s%s, ignoring: %m", root, image_class_release_info[image_class].release_file_directory);
 
-        r = -ENOENT;
         FOREACH_DIRENT(de, extension_release_dir, return -errno) {
                 int k;
 
@@ -228,12 +228,10 @@ int open_extension_release(
                 /* We already found what we were looking for, but there's another candidate? We treat this as
                  * an error, as we want to enforce that there are no ambiguities in case we are in the
                  * fallback path. */
-                if (r == 0) {
-                        r = -ENOTUNIQ;
-                        break;
-                }
+                if (found)
+                        return -ENOTUNIQ;
 
-                r = 0; /* Found it! */
+                found = true;
 
                 if (ret_fd)
                         fd = TAKE_FD(extension_release_fd);
@@ -244,8 +242,8 @@ int open_extension_release(
                                 return -ENOMEM;
                 }
         }
-        if (r < 0)
-                return r;
+        if (!found)
+                return -ENOENT;
 
         if (ret_fd)
                 *ret_fd = TAKE_FD(fd);