libxfs: when creating a file in a directory, set the project id based on the parent

libxfs: when creating a file in a directory, set the project id based on the parent

When we're creating a file as a child of an existing directory, use
xfs_get_initial_prid to have the child inherit the project id of the
directory if the directory has PROJINHERIT set, just like the kernel
does.  This fixes mkfs project id propagation with -d projinherit=X when
protofiles are in use.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>