Add changes string to XML reports

There was a change (gerrit change I590e21ab771290380315adeb2c8e28438e90939f)
that added the changes in JSON.stringified format to the test title. Jenkins
really needs that to tell selser tests apart, so now our JUnit output has it
also.

Change-Id: I0249772a14c6447b9d8ff1e88efec760ea817a0f