multipathd: improve "add missing path" handling

multipathd: improve "add missing path" handling

Only add devices that have been properly initialized by pathinfo().
For others, increase the path check interval to avoid useless checks
of devices which are probably not meant to be multipathed anyway.

The check for pp->initialized != INIT_MISSING_UDEV is redundant,
as check_path() returns early in all other cases. Replace it by a
check for INIT_FAILED, in case we ever add more init states.

Suggested-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Martin Wilck <mwilck@suse.com>