fix logical mistake

Signed-off-by: Daniel Osypenko <dosypenk@redhat.com>

ocs_ci/utility/prometheus.py

@@ -330,7 +330,7 @@ def __init__(self, user=None, password=None, threading_lock=None):
  Args:
  user (str): OpenShift username used to connect to API
  """
- if not threading_lock:
+ if threading_lock is None:
  raise NoThreadingLockUsedError(
  "using threading.Lock object is mandatory for PrometheusAPI class"
  )