tmpfiles: fix file descriptor leak

Detected by "cppcheck"
diff --git a/src/tmpfiles.c b/src/tmpfiles.c
index a6b8f85..21bf44d 100644
--- a/src/tmpfiles.c
+++ b/src/tmpfiles.c
@@ -157,6 +157,7 @@
                 }
         }
 
+        fclose(f);
         return;
 
 fail: