Check vpn client template exists

src/freedombone-app-vpn

 
     user_vpn_cert_file=/home/$username/$OPENVPN_KEY_FILENAME
 
+    if [ ! -f /usr/share/doc/openvpn/examples/sample-config-files/client.conf ]; then
+        echo $'No VPN client template found'
+        exit 429823
+    fi
+
     cp /usr/share/doc/openvpn/examples/sample-config-files/client.conf $user_vpn_cert_file
     sed -i "s|remote .*|remote $DEFAULT_DOMAIN_NAME 1194|g" $user_vpn_cert_file
     sed -i 's|;user nobody|user nobody|g' $user_vpn_cert_file