[PATCH] Add udev rule to add by-path links for xen vbd devices Xen vbd (virtual block devices) are the storage devices used on xen instances. On AL1 these devices had by-path symlinks in /dev/disk which were created by a udev rule in 60-persistent-storage.rules, however this rule required that the ID_PATH attribute be set. This attribute isn't set by the systemd version shipped in AL2 (v219) as it's setting for the xen device was removed in v184. Thus add the 51-ec2-xen-vbd-devices.rules udev rule to preserve this behaviour. Note the rule sets the ID_PATH attribute but relies on the existing rule to generate the symlinks.
AL1 output: $ ls -l /dev/disk/by-path total 0 lrwxrwxrwx 1 root root 10 May 18 23:45 xen-vbd-51712 -> ../../xvda lrwxrwxrwx 1 root root 11 May 18 23:45 xen-vbd-51712-part1 -> ../../xvda1
AL2 output without patch: $ ls -l /dev/disk/by-path
AL2 output with patch: ]$ ls -l /dev/disk/by-path total 0 lrwxrwxrwx 1 root root 10 May 18 23:48 xen-vbd-51712 -> ../../xvda lrwxrwxrwx 1 root root 11 May 18 23:48 xen-vbd-51712-part1 -> ../../xvda1
