Btrfs: Turn off extent state leak debugging

The extent_io.c code has a #define to find and cleanup extent state leaks
on module unmount.  This adds a very highly contended spinlock to a
hot path for most FS operations.

Turn it off by default.  A later changeset will add a .config option
for it.
Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent_io.c

@@ -30,7 +30,7 @@ static struct kmem_cache *extent_buffer_cache;
 static LIST_HEAD(buffers);
 static LIST_HEAD(states);
 
-#define LEAK_DEBUG 1
+#define LEAK_DEBUG 0
 #ifdef LEAK_DEBUG
 static spinlock_t leak_lock = SPIN_LOCK_UNLOCKED;
 #endif