Use grep instead of sed for boolean checks

Author: teacup-on-rockingchair

linux_os/guide/system/software/gnome/gnome_login_screen/gnome_gdm_disable_unattended_automatic_login/bash/shared.sh

@@ -1,11 +1,9 @@
 # platform = multi_platform_sle,multi_platform_slmicro
 
-if ! (sed -n '/^DISPLAYMANAGER_AUTOLOGIN=\"\"/p' /etc/sysconfig/displaymanager)
-then
+if ! grep -q '^DISPLAYMANAGER_AUTOLOGIN=""' /etc/sysconfig/displaymanager; then
   sed -i "s/^DISPLAYMANAGER_AUTOLOGIN=.*/DISPLAYMANAGER_AUTOLOGIN=\"\"/g" /etc/sysconfig/displaymanager
 fi
 
-if ! (sed -n '/^DISPLAYMANAGER_PASSWORD_LESS_LOGIN=\"no\"/p' /etc/sysconfig/displaymanager)
-then
+if ! grep -q '^DISPLAYMANAGER_PASSWORD_LESS_LOGIN="no"' /etc/sysconfig/displaymanager; then
   sed -i "s/^DISPLAYMANAGER_PASSWORD_LESS_LOGIN=.*/DISPLAYMANAGER_PASSWORD_LESS_LOGIN=\"no\"/g" /etc/sysconfig/displaymanager
 fi