BUG/MINOR: thread: fix a typo in the debug code

__spin_unlock() used to call RWLOCK_WRUNLOCK() to unlock in the
debug code. It's harmless as they happen to be identical.
diff --git a/include/common/hathreads.h b/include/common/hathreads.h
index 3524ef1..853c9f1 100644
--- a/include/common/hathreads.h
+++ b/include/common/hathreads.h
@@ -542,7 +542,7 @@
 	l->info.last_location.file     = file;
 	l->info.last_location.line     = line;
 
-	__RWLOCK_WRUNLOCK(&l->lock);
+	__SPIN_UNLOCK(&l->lock);
 	HA_ATOMIC_ADD(&lock_stats[lbl].num_write_unlocked, 1);
 }