Nodes unable resolve hosts when experimental mode is used

[Alexander Kurenyshev]

Steps to reproduce:
1. Setup master node
2. Enable 'experimental' in Nailgun
3. Restart Nailgun
4. Create cluster in ha mode with 1 controller
5. Define DNS and NTP servers as master node IP
6. Deploy, run OSTF

Expected behaviour:
Everything is ok

Actual behaviour:
One of the OSTF tests has failed.
AssertionError: Failed tests, fails: 1 should fail: 0 failed tests name: [{u'Check DNS resolution on compute node (failure)': u'Instance is not reachable by IP. Please refer to OpenStack logs for more details.'}

Fuel used:
"build_id": "2015-04-13_22-54-31",
"ostf_sha": "c2a76a60ec4ebbd78e508216c2e12787bf25e423",
"build_number": "310",
"release_versions": {"2014.2-6.1": {"VERSION": {"build_id": "2015-04-13_22-54-31",
"ostf_sha": "c2a76a60ec4ebbd78e508216c2e12787bf25e423",
"build_number": "310",
"api": "1.0",
"nailgun_sha": "d22c074dec091e5ddd8ea3003c37665058303cd5",
"openstack_version": "2014.2-6.1",
"production": "docker",
"python-fuelclient_sha": "9208ff4a08dcb674ce2df132399a5aa3ddfac21c",
"astute_sha": "d96a80b63198a578b2c159edbd76048819039eb0",
"feature_groups": ["mirantis"],
"release": "6.1",
"fuelmain_sha": "335d3ed09ed79bd37e1f7a90442c4831c8845582",
"fuellib_sha": "8b80657e9ceed8d59c2dff1c11e1481c7e69380e"}}},
"auth_required": true,
"api": "1.0",
"nailgun_sha": "d22c074dec091e5ddd8ea3003c37665058303cd5",
"openstack_version": "2014.2-6.1",
"production": "docker",
"python-fuelclient_sha": "9208ff4a08dcb674ce2df132399a5aa3ddfac21c",
"astute_sha": "d96a80b63198a578b2c159edbd76048819039eb0",
"feature_groups": ["experimental",
"mirantis"],
"release": "6.1",
"fuelmain_sha": "335d3ed09ed79bd37e1f7a90442c4831c8845582",
"fuellib_sha": "8b80657e9ceed8d59c2dff1c11e1481c7e69380e"