oo-trap-user: make gear login syslog optional

Introduce node.conf setting SYSLOG_GEAR_LOGIN=true so that by default,
logging gear logins to syslogs occurs on a new install, but existing
nodes and node.conf files don't have this start happening without
intervention.

Bug 1134139 - [RFE] Track real person for gear SSH logins
https://bugzilla.redhat.com/show_bug.cgi?id=1134139