Re-enable tests in the buildscripts_test suite

A number of tests are disabled in the python buildscripts test suite.

Apart from buildscripts/tests/test_remote_operations.py, which requires ssh to be enabled locally, the other tests should be able to run with a new deployment of the toolchain and/or the modifying the file paths used in tests to use os.path.join instead of hardcoding in POSIX strings.