Only display home free space

The rest is redundant.  On a healthy system, / does not need to be
watched so closely and libvirt/images uses sparse files so the info is
not so accurate.

dotfiles/config/i3status/config

 order += "battery 1"
 order += "load"
 order += "cpu_usage"
-order += "disk /var/lib/libvirt/images"
-order += "disk /"
 order += "disk /home"
 order += "volume master"
 order += "tztime local"
     format = "%Y-%m-%d %H:%M"
 }
 
-disk "/var/lib/libvirt/images" {
-    format = "i:%avail"
-    threshold_type = "gbytes_avail"
-    low_threshold = 2
-}
-
-disk "/" {
-    format = "/:%avail"
-    threshold_type = "gbytes_avail"
-    low_threshold = 2
-}
-
 disk "/home" {
     format = "~:%avail"
     threshold_type = "gbytes_avail"