UnitTestImageWriter.cpp prints thousands of lines

While trying to track down a failure in this build, I got swamped in thousands of lines of log statements:

459: 2020-05-18 21:14:33.257 (   0.868s) [main thread     ]UnitTestImageWriter.cxx:57    Info| Row[14][(85),(85),(0),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),]
459: 2020-05-18 21:14:33.257 (   0.868s) [main thread     ]UnitTestImageWriter.cxx:57    Info| Row[15][(85),(0),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),(85),]
459: 2020-05-18 21:14:33.259 (   0.869s) [main thread     ]UnitTestImageWriter.cxx:57    Info| Row[0][(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),]
459: 2020-05-18 21:14:33.259 (   0.869s) [main thread     ]UnitTestImageWriter.cxx:57    Info| Row[1][(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(21845),(0),]

I suspect that now this test is passing reliably, these statements can be removed.

Low priority, obviously, but would be convenient.