Disable debug messages when running unit tests

Some runs started to fail due to large sub_unit.log files. We should
reduce their size. The easy way to achieve this is to disable INFO
messages that are filling our logs.

Change-Id: I6b3d3a4498593b6b5635d7eded4f9f88c84e5da0
Closes-Bug: 1316610
Merge "Disable debug messages when running unit tests"