examine: allows to examine a disk metadata on non-metadata compliant systems

examine: allows to examine a disk metadata on non-metadata compliant systems

Allow for loading metadata from disk attached to non-metadata compliant
system. Affects mdadm --examine and guess_super.

Added ignore_hw_compat in supertype to pass information to load_super
handler. If ignore_hw_compat is set the handler should load metadata
also from disks that do not comply with metadata requirements (i.e. disk is not
attached to native controller, etc).

Signed-off-by: Marcin Labun <marcin.labun@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>