After kernel-3.13.0-41, wireless script checks wrong sys file.

[katsu]

[TEST CASE]
* on a laptop machine with a ac adapter connect & wireless interface run:
1. ac adapter disconnect
2. $ tail /var/log/pm-powersave.log & $ iwconfig

[Actual Result]
* wireless power management does not "ON"

$ tail /var/log/pm-powersave.log
--->---> snip --->---> snip --->---> snip --->---> snip --->--->
Running hook /usr/lib/pm-utils/power.d/wireless true:
cat: /sys/class/net/wlan0/device/enabled: No such file or directory
/usr/lib/pm-utils/power.d/wireless true: success.
--->---> snip --->---> snip --->---> snip --->---> snip --->--->

$ iwconfig
wlan0 IEEE 802.11bgn ESSID:"xxxxxxxxx"
--->---> snip --->---> snip --->---> snip --->---> snip --->--->
          Power Management:off
--->---> snip --->---> snip --->---> snip --->---> snip --->--->

[Expected Result]
$ tail /var/log/pm-powersave.log
--->---> snip --->---> snip --->---> snip --->---> snip --->--->
Running hook /etc/pm/power.d/wireless true:
Turning powersave for wlan0 on...Done.
/etc/pm/power.d/wireless true: success.
--->---> snip --->---> snip --->---> snip --->---> snip --->--->

$ iwconfig
wlan0 IEEE 802.11bgn ESSID:"xxxxxxxxx"
--->---> snip --->---> snip --->---> snip --->---> snip --->--->
          Power Management:on
--->---> snip --->---> snip --->---> snip --->---> snip --->--->

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.2 LTS
Release: 14.04
Codename: trusty

$ uname -a
Linux xxxxxxx 3.13.0-49-generic #81-Ubuntu SMP Tue Mar 24 19:29:48 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/modprobe.d/ath9k_powersave.conf
options ath9k ps_enable=1

$ apt-cache policy pm-utils
pm-utils:
  インストールされているバージョン: 1.4.1-13ubuntu0.1
  候補: 1.4.1-13ubuntu0.1
  バージョンテーブル:
 *** 1.4.1-13ubuntu0.1 0
        500 http://www.ftp.ne.jp/Linux/packages/ubuntu/archive/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.4.1-13 0
        500 http://www.ftp.ne.jp/Linux/packages/ubuntu/archive/ trusty/main amd64 Packages

[katsu (katsukatsu-deactivatedaccount)]

[the root cause]
$ apt-get changelog linux-image-3.13.0-41-generic
--->---> snip --->---> snip --->---> snip --->---> snip --->--->
* PCI: Rename sysfs 'enabled' file back to 'enable'
    - LP: #1393477
--->---> snip --->---> snip --->---> snip --->---> snip --->--->

[recommendation 1]
* revert 17-fix-wireless-hook.patch in pm-utils package.

  * debian/patches/17-fix-wireless-hook.patch: Fix typo in wireless
    hook (LP: #1299975).

[recommendation 2]
$ diff -Nur wireless.orig wireless
--- wireless.orig 2015-04-12 13:52:04.911478886 +0900
+++ wireless 2015-04-12 13:52:37.791641939 +0900
@@ -19,8 +19,12 @@
     [ -L "/sys/class/net/$1/device/driver" ] || return 1
     # Skip if not a wireless card.
     [ -d "/sys/class/net/$1/wireless" ] || return 1
+ # Confirm sysfs filename. (enable or enabled)
+ [ -e "/sys/class/net/$1/device/enable" ] && sysfsname="enable"
+ [ -e "/sys/class/net/$1/device/enabled" ] && sysfsname="enabled"
     # Also don't do anything if the device is disabled
- [ "$(cat /sys/class/net/$1/device/enabled)" = "1" ] || return 1
+ [ "$(cat /sys/class/net/$1/device/$sysfsname)" = "1" ] || return 1
+ unset sysfsname
     driver="$(readlink "/sys/class/net/$1/device/driver")"
     driver=${driver##*/}
     case $driver in