refactor: improve random password generation in install_config.sh

The code change refactors the random password generation in the `install_config.sh` file. Instead of using `tr -dc A-Za-z0-9_ < /dev/urandom | head -c 8 | xargs`, it now uses `tr -dc 'A-Za-z0-9_' < /dev/urandom 2>/dev/null | head -c 8 | xargs`. This change improves the reliability and security of generating random passwords.

lgsm/modules/install_config.sh

@@ -64,7 +64,7 @@ fn_default_config_local() {
 # PASSWORD to random password
 fn_set_config_vars() {
 	if [ -f "${servercfgfullpath}" ]; then
-		random=$(tr -dc A-Za-z0-9_ < /dev/urandom | head -c 8 | xargs)
+		random=$(tr -dc 'A-Za-z0-9_' < /dev/urandom 2>/dev/null | head -c 8 | xargs)
 		servername="LinuxGSM"
 		rconpass="admin${random}"
 		echo -e "changing hostname."