tests: remove useless test

`test_mon_host_line_has_correct_value()` will cover this test in
anycase. It doesn't worth to have a dedicated test for this.

Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

tests/functional/tests/test_install.py

@@ -23,9 +23,6 @@ class TestInstall(object):
 
 class TestCephConf(object):
 
-    def test_ceph_config_has_mon_host_line(self, node, File):
-        assert File(node["conf_path"]).contains("^mon host = .*$")
-
     def test_mon_host_line_has_correct_value(self, node, host):
         mon_host_line = host.check_output("grep 'mon host = ' /etc/ceph/{cluster}.conf".format(cluster=node['cluster_name']))  # noqa E501
         result = True