[evlatests] Update on L352 round-trip meters

[Vivek Dhawan]

Since February 2, the meters have been under scrutiny.

After various twists and turns, (sign changes and scale-
factor changes) 3 of them have settled down -mostly.
I wont go over the history unless someone thinks there
are lessons to learn.

The current status: since Feb 24, all 4 meters are on
antenna 13 (long fiber).

3d: seems to be the best of the lot. (But had jumps
    in its output here at the AOC test setup; no jumps
    since it was moved to the EVLA, feb 15th.)

40: has opposite sign to 3d.  Also has jumps in its
    output a few times a day, of a few ps. Otherwise
    it tracks 3d.

51: Working well since reset on Feb 24. Has opposite sign
    to 3d, but tracks it well.

52: Odd man out - has a response that is clearly different
    from the others by ~10%. Same sign as 3d.

Vivek.