dmsetup: fix udev event handling for create

With newer kernels (>5.13)  DM_CREATE no longer generates
uevent for DM devices without table.
There are even no sysfs block device entries in such case,
although device has asigned major:minor and it is being listed
by 'dmsetup info'.

So this patch calculates amount of 'table' lines and in case
no table line comes from cmdline or stdin - waiting on cookie
is avoided generically instead of disabling just case with
option --notable - which then also skipped handling of an
option --addnodeoncreate (which is however historical and
should be avoided)

As a result there should be no leaking udev cookies and endlessly
waiting commands like this:

dmsetup create mytestdev  </dev/null

0 files changed, 0 insertions, 0 deletions