Fix an early return in ctld UCL parser

If the UCL ctld parser encountered a port that used the CTL
ioctl device, it fell into a special case that had an erroneous
early return. This caused all configuration in the target
following the port attribute to be skipped. Fix this by replacing
the return with a continue so that the rest of the config is
parsed correctly.

Sponsored by: Dell EMC Isilon
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D31703
Reviewed by: bapt