Integration tests cannot run in parallel

[zachcran]

Is your feature request related to a problem? Please describe.
The integration tests under tests/scripts do not each work in their own testing space, so they cannot be parallelized. For example, test_CMaizePrivateDepend2.sh and test_CMaizePrivateDepend2_w_all_deps will each use the same src/ and install/ directories. This means that they might grab partial packages or if called with --clean will delete files the other tests may be using.

Describe the solution you'd like
Each test should download the files they need, create build artifacts, and install into a directory unique to that test. These test subdirectories can probably just have the same name as the test, since the test/test script file names need to be unique anyways.

The test scripts are not currently set up in a way that allows this type of setup easily. However, I think the scripts could be modified to work with relative paths or take the WORKSPACE variable as a command line argument. This would either allow them to work from the current directory (would need to be set before calling the script) or allow us to provide which directory the test should occur in, respectively.

Describe alternatives you've considered
Continue to perform the integration tests serially.