Btrfs: account for orphan inodes properly during cleanup

Dave sent me a panic where we were doing the orphan cleanup and panic'ed
trying to release our reservation from the orphan block rsv.  The reason for
this is because our orphan block rsv had been free'd out from underneath us
because the transaction commit found that there were no orphan inodes
according to its count and decided to free it.  This is incorrect so make
sure we inc the orphan inodes count so the accounting is all done properly.
This would also cause the warning in the orphan commit code normally if you
had any orphans to cleanup as they would only decrement the orphan count so
you'd get a negative orphan count which could cause problems during runtime.
Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>