ddns-scripts: fix logging bug

Fixes issue #11282, this patch was provided by PaulFertser on the #openwrt
IRC.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

net/ddns-scripts/files/dynamic_dns_functions.sh

@@ -282,11 +282,11 @@ write_log() {
 	[ $__LEVEL -eq 7 ] && return	# no syslog for debug messages
 	__CMD=$(echo -e "$__CMD" | tr -d '\n' | tr '\t' '     ')        # remove \n \t chars
 	[ $__EXIT  -eq 1 ] && {
-		eval "$__CMD"	# force syslog before exit
+		eval '$__CMD'	# force syslog before exit
 		exit 1
 	}
 	[ $use_syslog -eq 0 ] && return
-	[ $((use_syslog + __LEVEL)) -le 7 ] && eval "$__CMD"
+	[ $((use_syslog + __LEVEL)) -le 7 ] && eval '$__CMD'
 
 	return
 }