marsadm: fix incomplete syslog messaging
marsadm: workaround concept bug in _get_actual_primary(), deprecate it

The conceptual bug was leading to systematic false-positive failures in the
old test_suite. These failures were depeding on the _names_ of the
involved hosts: just run it on a pair of differently named hosts
following different naming conventions, and 50 out of 90 testcases
were failing false-positively.