fixed a few problems in ssc tests

Created by: JasonRuonanWang

@chuckatkins Could you help check the cmake stuff and see if there is any smarter ways of doing this? Basically what I needed here is that I need to delete the .ssc file that is generated from previous test runs before running another time. However, cmake does not allow me to run multiple commands in adding a single test. This is a workaround I found on stackoverflow, but it looks quite ugly. Thanks.