udev: 56-hpmud.rules should not run usb_id for all USB devices out there

The pre-history could be seen in this issue first reported to systemd/udev: https://github.com/systemd/systemd/issues/2414

In short, the HPLIP's `56-hpmud.rules` udev rules file runs `usb_id` unconditionally for all USB devices (but only on "add" event), which 1) affects execution of follow-up rules and 2) makes the whole process yield different results on "add" and "change" events.

Ultimately, this leads to unexpectedly changing attributes and device node symlinks for USB-ATA disk devices (completely unrelated to HPLIP) after a "change" event.

Observing the rule file itself, I suspect that a GOTO to rule file end is missing:

--- a/56-hpmud.rules 2015-12-07 04:28:15.000000000 +0300
+++ b/56-hpmud.rules 2016-01-24 12:32:24.708201975 +0300
@@ -3,6 +3,7 @@
 ACTION!="add", GOTO="hpmud_rules_end"
 SUBSYSTEM=="ppdev", OWNER="root", GROUP="lp", MODE="0664"
 SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", GOTO="hpmud_usb_rules"
+GOTO="hpmud_rules_end"

 LABEL="hpmud_usb_rules"