tests: sanitycheck: Testcases for load_from_file and apply_filters

test_testsuite_class.py: Added testcases for load_From_file and
apply_filters functions of Class Testsuite.
conftest.py: Modified class_testsuite fixture to create the
outdir as temporary directory which gets deleted after execution
of testcases.
test_data/sanitycheck.csv: load_from_file function uses this
customized file to load the failed or last run testcases.
test_data/sanitycheck_keyerror.csv: file used by
test_load_from_file function to raise the appropriate error
if there is a keyerror.
scripts/requirements-build-test.txt: added mock & csv python libraries

Signed-off-by: Aastha Grover <aastha.grover@intel.com>
6 files changed