mandos-ctl: Refactor: fix confusion about values_to_set/values_to_get
* mandos-ctl (TestPropertySetterCmd.runTest): Generalize to work on any command regardless of what combination of values_to_set or values_to_get attributes it has. (TestPropertySetterCmd.run_command): Remove. (TestEnableCmd, TestDisableCmd, TestBumpTimeoutCmd, TestStartCheckerCmd, TestStopCheckerCmd, TestApproveByDefaultCmd, TestDenyByDefaultCmd): Change "values_to_set" to "values_to_get", since that is what is intended. (TestPropertySetterValueCmd): Remove; all inheritors changed to inherit from TestPropertySetterCmd.