Fix start avocado if SCT_NEW_CONFIG env var was set (#950)
Fix start avocado if SCT_NEW_CONFIG env var was set (#950)

If start hydra with SCT_NEW_CONFIG env var, avocado not started due to issue
ocado.test:
avocado.test: Temporary dir: /var/tmp/avocado_mTXVFE
avocado.test:
avocado.test: Variant 1:    /
avocado.test:
avocado.test: Job ID: 3600d8e536669994d15c9c1a0fdf6178d4d88023
avocado.test:
avocado.test: /usr/lib/python2.7/site-packages/elasticsearch/connection/http_urllib3.py:111: UserWarning: Connecting to 746f0ad652a3447d83b1572f657c67cb.us-east-1.aws.found.io using SSL with verify_certs=False is insecure.
avocado.test:   'Connecting to %s using SSL with verify_certs=False is insecure.' % host)
avocado.test: PARAMS (key=timeout, path=*, default=None) => 650000
avocado.test: START 1-longevity_test.py:LongevityTest.test_custom_time
avocado.test: Process Process-1:
avocado.test: Traceback (most recent call last):
avocado.test:   File "/usr/lib64/python2.7/multiprocessing/process.py", line 258, in _bootstrap
avocado.test:     self.run()
avocado.test:   File "/usr/lib64/python2.7/multiprocessing/process.py", line 114, in run
avocado.test:     self._target(*self._args, **self._kwargs)
avocado.test:   File "/usr/lib/python2.7/site-packages/avocado/core/runner.py", line 237, in _run_test
avocado.test:     instance = loader.load_test(test_factory)
avocado.test:   File "/usr/lib/python2.7/site-packages/avocado/core/loader.py", line 263, in load_test
avocado.test:     test_instance = test_class(**test_parameters)
avocado.test:   File "/sct/sdcm/tester.py", line 155, in __init__
avocado.test:     self.params.verify_configuration()
avocado.test:   File "/sct/sdcm/sct_config.py", line 940, in verify_configuration
avocado.test:     raise ValueError("Unsupported environment variables were used:\n\t - {}".format("\n\t - ".join(output)))
avocado.test: ValueError: Unsupported environment variables were used:
avocado.test: 	 - SCT_NEW_CONFIG=yes
amoskong/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests,amoskong/scylla-cluster-tests,scylladb/scylla-cluster-tests