InSAR golden tests should fail if the reference point changes

[jhkennedy]

In ASFHyP3/hyp3-gamma#328 the golden InSAR tests were not sensitive enough to notice the reference point had changed. This could be due to:

1. our current pairs not being sensitive to a reference point change (expect no actual change in the data)
2. our current thresholds are set high enough we'd not notice (change was there but ignored)

We should check our current pairs and see if there are changes due to the reference point change in ASFHyP3/hyp3-gamma#328, or pick a pair that shows large changes to add to the test suite.

Either way, we should catalog in this issue specifically:

• what product TIFFs we expect to change
• the level of those changes

for any pairs we expect to fail.

[cirrusasf]

change reference point will impact unw_phase.tif, unw_phase.png, los_disp.tif, vert_disp.tif. As far as how difference between unwrapped-phase tif files produced with reference point (0,0) and highest coherence reference point, it depends. It does not have certain answer.

[cirrusasf]

The unwrapped-phase (unw) difference between prod and test is equal to the phase value at the reference point. For example, for the pair "S1A_IW_SLC__1SDV_20200203T172103_20200203T172122_031091_03929B_3048",
"S1A_IW_SLC__1SDV_20200110T172104_20200110T172123_030741_03864E_A996", The phase value at the reference point is 5.95494, so unw_prod =unw_test + 5.95494 . The diff image is a plain image, each pixel value of the diff image is equal to the phase at the reference point.