tests should only run when applicable for adv-sg zone in such env

##### ISSUE TYPE

* Documentation Report
* testing/CI

##### COMPONENT NAME

~~~
marvin
~~~

##### CLOUDSTACK VERSION

~~~
4.18
~~~

##### CONFIGURATION

~~~
advanced zone with security groups.
~~~

##### OS / ENVIRONMENT

##### SUMMARY

when an advanced zone with security groups is used to test for regressions, a lot of errors occur.
an example
```
ERROR: test suite for
----------------------------------------------------------------------
Traceback (most recent call last):
File "/usr/local/lib/python3.6/site-packages/nose/suite.py", line 210, in run
self.setUp()
File "/usr/local/lib/python3.6/site-packages/nose/suite.py", line 293, in setUp
self.setupContext(ancestor)
File "/usr/local/lib/python3.6/site-packages/nose/suite.py", line 316, in setupContext
try_run(context, names)
File "/usr/local/lib/python3.6/site-packages/nose/util.py", line 471, in try_run
return func()
File "/marvin/tests/smoke/test_router_dns.py", line 92, in setUpClass
zoneid=cls.zone.id)
File "/usr/local/lib/python3.6/site-packages/marvin/lib/base.py", line 3562, in create
return Network(apiclient.createNetwork(cmd).__dict__)
File "/usr/local/lib/python3.6/site-packages/marvin/cloudstackAPI/cloudstackAPIClient.py", line 2981, in createNetwork
response = self.connection.marvinRequest(command, response_type=response, method=method)
File "/usr/local/lib/python3.6/site-packages/marvin/cloudstackConnection.py", line 381, in marvinRequest
raise e
File "/usr/local/lib/python3.6/site-packages/marvin/cloudstackConnection.py", line 376, in marvinRequest
raise self.__lastError
File "/usr/local/lib/python3.6/site-packages/marvin/cloudstackConnection.py", line 310, in __parseAndGetResponse
response_cls)
File "/usr/local/lib/python3.6/site-packages/marvin/jsonHelper.py", line 155, in getResultObj
raise cloudstackException.CloudstackAPIException(respname, errMsg)
marvin.cloudstackException.CloudstackAPIException: Execute cmd: createnetwork failed, due to: errorCode: 431, errorText:Only shared guest network can be created in security group enabled zone
```

this is not necessary as we know beforehand that these tests will fail.
Tests need to be properly tagged to not run in these environments.

##### STEPS TO REPRODUCE

~~~

~~~

##### EXPECTED RESULTS

~~~
test will not run
~~~

##### ACTUAL RESULTS

~~~
test runs and fails
~~~

Beginne mit marvin/tests/smoke/test_router_dns.py und dem im Bericht gezeigten TestRouterDns-Setup. Untersuche anschließend die anderen Regressionstests, die in einer erweiterten Zone mit Sicherheitsgruppen fehlschlagen. Die Aufgabe ist erledigt, wenn Tests, die in dieser Umgebung nicht anwendbar sind, übersprungen werden, statt ausgeführt zu werden und fehlschlagen; überprüfe das Verhalten mit der betroffenen Testsuite.

Vom Indexierungsmodell aus dem Issue-Text verfasst.