raw-posix: raw_co_get_block_status() return value

raw-posix: raw_co_get_block_status() return value

Instead of generating the full return value thrice in try_fiemap(),
try_seek_hole() and as a fall-back in raw_co_get_block_status() itself,
generate the value only in raw_co_get_block_status().

While at it, also remove the pnum parameter from try_fiemap() and
try_seek_hole().

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1414148280-17949-3-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>