xfs: evict CoW fork extents when performing finsert/fcollapse

When we perform an finsert/fcollapse operation, cancel all the CoW
extents for the affected file offset range so that they don't end up
pointing to the wrong blocks.

Reported-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>