For improved flexibility and maintainability.
* Update tasks in node role to use 'group_name_master' variable instead
of hardcoded 'master' group name
* Update tasks in master role to use 'group_name_master' variable instead
of hardcoded 'master' group name
* Update tasks in post role to use 'group_name_master' variable instead of
hardcoded 'master' group name
Signed-off-by: Christian Berendt <berendt@23technologies.cloud>
