Fix incorrect command formulation

Mitigation of an error where instead of no argument an "empty argument"
was passed to `lscpu`

	lscpu ''

vs.

	lscpu

(cherry picked from commit a5bd254)

repos/system_upgrade/common/actors/scancpu/libraries/scancpu.py

@@ -12,7 +12,7 @@
 
 def _get_lscpu_output(output_json=False):
     try:
-        result = run(['lscpu', '-J' if output_json else ''])
+        result = run(['lscpu'] + (['-J'] if output_json else []))
         return result.get('stdout', '')
     except (OSError, CalledProcessError):
         api.current_logger().debug('Executing `lscpu` failed', exc_info=True)