Btrfs: run delayed directory updates during log replay

commit b6305567e7d31b0bec1b8cb9ec0cadd7f7086f5f upstream.

While we are resolving directory modifications in the
tree log, we are triggering delayed metadata updates to
the filesystem btrees.

This commit forces the delayed updates to run so the
replay code can find any modifications done.  It stops
us from crashing because the directory deleltion replay
expects items to be removed immediately from the tree.

Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>