Also change both proxy-server and object-server
.conf templates to test if log_udp_server and
log_udp_port are nil, instead of an empty string.
Testing for an empty string would have retruned
true if set to 'undef' - for futer parser compat.
Change-Id: Idac805f628dbec70a4adb6a1c021d85a743fdb72