[evlatests] test of automatic level setting

[Ken Sowinski]

We now have power meters in IFs A and C for all five antennas
so the system was modified to set the attenuators to servo
the power to a desired value for IFs A and C.  This was tested
at all bands, including P band, using all antennas but 24, and
seems to work as expected.  P band is available only on antenna 14.

In each case I examined the detector outputs, sampler output RMS,
and T5 parameters for all the antennas after setting up the antenna
at each band.  Before commiting the changes I want to think a
bit more about the proper set points for cases where the receiver
provides less than 4 GHz as seen at the downconverter, especially
the case of P band.

Once the changes are in place we should be aware that there may
be systematic differences in the performance of the two IF pairs.