Update services_ntpd.php

Add validation for the case of no server specified, fall back to pool.ntp.org
remove openbgpd bits from system_gateways_edit and system.inc. The package
match is case-sensitive and hasn't matched the openbgpd package's name in
at least 5 years, so it doesn't do anything. It's far from functional in
any useful manner even fixing that issue.
Fix variable name
Fix filename
Merge pull request #1219 from nagyrobi/patch-13