Add explanation about the default value of sysctl key

machdep.pwraction
ok jmc millert

src/etc/etc.amd64/sysctl.conf

@@ -1,4 +1,4 @@
 #machdep.allowaperture=2	# See xf86(4)
 #machdep.kbdreset=1		# permit console CTRL-ALT-DEL to do a nice halt
 #machdep.lidaction=0		# 1=suspend, 2=hibernate laptop upon lid closing
-#machdep.pwraction=1		# ACPI power button action: 0=none, 2=suspend
+#machdep.pwraction=1		# ACPI power button action: 0=none, 1=shutdown, 2=suspend