perf: release lock after transaction in perffncachewrite

The transaction should be closed within the lock.

contrib/perf.py

@@ -575,8 +575,8 b' def perffncachewrite(ui, repo, **opts):'
         s.fncache._dirty = True
         s.fncache.write(tr)
     timer(d)
+    tr.close()
     lock.release()
-    tr.close()
     fm.end()
 
 @command('perffncacheencode', formatteropts)