rules: Add by-id symlinks for persistent memory

rules: Add by-id symlinks for persistent memory

This patch adds a by-id symlink to persistent memory namespace if it
exports a uuid attribute. The result looks like the following example:

 # ls -l /dev/disk/by-id/*
 lrwxrwxrwx 1 root root 13 Jul  9 15:24 pmem-206dcdfe-69b7-4e86-a01b-f540621ce62e -> ../../pmem1.2
 lrwxrwxrwx 1 root root 13 Jul  9 15:24 pmem-73840bf1-4e74-4ba4-a9c8-8248934c07c8 -> ../../pmem1.1
 lrwxrwxrwx 1 root root 13 Jul  9 15:24 pmem-8137bdfd-3c4d-4b26-b326-21da3d4cd4e5 -> ../../pmem1.4
 lrwxrwxrwx 1 root root 13 Jul  9 15:24 pmem-f43d1b6e-3300-46cb-8afc-06d66a7c16f6 -> ../../pmem1.3

Signed-off-by: Keith Busch <keith.busch@intel.com>