Fall back to using cobra centers when no cobra_target info available.

There are times when we want to take an MCS exposure and get fiber matches, but without knowing where the cobras are expected to be – there is no

information from the fpsActor. In that case populate the expected positions for the matching routines with the cobra centers.

Basically,

should assign fiber matches, but not fabricate opdb table rows (like for cobra_target) which it has no business touching.