rhsm_release: improve the execution of subscription-manager (#6669)
- pass the arguments to run_command() directly as list, rather than
joining the arguments to string, which run_command() will need to
split again
- disable the expansions of variables, as there are none
Adapt the unit test to the different way run_command() is called,
factorizing the kwargs for run_command() so there is less repetition.
There should be no behaviour changes.
(cherry picked from commit 74ffb29573)
Co-authored-by: Pino Toscano <ptoscano@redhat.com>
