An fallocate request without FALLOC_FL_KEEP_SIZE set can extend the
size of a file. Update the inode size after a successful fallocate.

Also invalidate the inode attributes after a successful fallocate
to ensure we pick up the latest attribute values (i.e., i_blocks).
Signed-off-by: NBrian Foster <bfoster@redhat.com>
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>