Applied tier0 and tier1 marks on unit tests and xmlrpc tests

Web UI tests were marked as tier1 tests.

The tier system is intended to be used together with CI system
to make sure the more complicated tests are being run only
when all of the basic functionality is working.

The system is using pytest's marker system. E.g. an invocation of
all tier1 tests with listing will look like:

    $ py.test -v -m tier1 ipatests

or in case of out of tree tests:

    $ ipa-run-tests -m tier1

Reviewed-By: Ales 'alich' Marecek <amarecek@redhat.com>

ipatests/test_cmdline/test_help.py

@@ -26,11 +26,13 @@ from six import StringIO
 
 from ipalib import api, errors
 from ipalib.plugins.user import user_add
+import pytest
 
 if six.PY3:
     unicode = str
 
 
+@pytest.mark.tier0
 class CLITestContext(object):
     """Context manager that replaces stdout & stderr, and catches SystemExit