Create: don't default to bitmap=internal when it is not supported

Create: don't default to bitmap=internal when it is not supported

For large arrays (component size > 100GB) if write-intent bitmap is not
enabled, then it is set by default to "internal", even if the metadata
format does support internal bitmaps, which causes Create to fail.

This patch adds checking if add_internal_bitmap is set in the
superswitch before setting bitmap_file to "internal".

Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>