Lowering hard drive idle timeout to 5 seconds from 20 seconds.

This change saves about 200mW of power on SSDs.

Change-Id: I7a7dfdbd7e264386d21da673b1906460ecf1c307

BUG= chromium-os:9180
TEST= ran vmstat & hdparm to see when the last read/write to the disk
happened and when the drive transitioned to standby state.  With this
change in place, on battery the hard drive transitioned to standby
state 5 seconds after the last read/write.

Review URL: http://codereview.chromium.org/5032002
diff --git a/laptop-mode-tools_1.52/etc/laptop-mode/laptop-mode.conf b/laptop-mode-tools_1.52/etc/laptop-mode/laptop-mode.conf
index ec038f4..d22eeab 100644
--- a/laptop-mode-tools_1.52/etc/laptop-mode/laptop-mode.conf
+++ b/laptop-mode-tools_1.52/etc/laptop-mode/laptop-mode.conf
@@ -232,7 +232,7 @@
 # for battery and for AC with laptop mode on.
 #
 LM_AC_HD_IDLE_TIMEOUT_SECONDS=20
-LM_BATT_HD_IDLE_TIMEOUT_SECONDS=20
+LM_BATT_HD_IDLE_TIMEOUT_SECONDS=5
 NOLM_HD_IDLE_TIMEOUT_SECONDS=7200