rules: set SYSTEMD_READY=0 on DM_UDEV_DISABLE_OTHER_RULES_FLAG=1 only…

… with ADD event (#2747)

The "SYSTEMD_READY=0" will cause automatic unmount
of mountpoint that is on top of such DM device
if this is used with multipath which sets
DM_UDEV_DISABLE_OTHER_RULES_FLAG in case
we have a CHANGE event thatcomes after DM multipath
device reload when one of the paths is down or up.

See https://bugzilla.redhat.com/show_bug.cgi?id=1312011

rules/99-systemd.rules.in

@@ -11,7 +11,7 @@ SUBSYSTEM=="tty", KERNEL=="tty[a-zA-Z]*|hvc*|xvc*|hvsi*|ttysclp*|sclp_line*|3270
 KERNEL=="vport*", TAG+="systemd"
 
 SUBSYSTEM=="block", TAG+="systemd"
-SUBSYSTEM=="block", ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}=="1", ENV{SYSTEMD_READY}="0"
+SUBSYSTEM=="block", ACTION=="add", ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}=="1", ENV{SYSTEMD_READY}="0"
 
 # Ignore encrypted devices with no identified superblock on it, since
 # we are probably still calling mke2fs or mkswap on it.