network verification shows duplicate dhcp warning for each node

not always reproduced, a screen snapshot is attached.

build info:
{"build_id": "2015-04-13_10-39-24", "ostf_sha": "c2a76a60ec4ebbd78e508216c2e12787bf25e423", "build_number": "169", "release_versions": {"2014.2-6.1": {"VERSION": {"build_id": "2015-04-13_10-39-24", "ostf_sha": "c2a76a60ec4ebbd78e508216c2e12787bf25e423", "build_number": "169", "api": "1.0", "nailgun_sha": "0435d55f252796e77791c62405af8f341338ae73", "openstack_version": "2014.2-6.1", "production": "docker", "python-fuelclient_sha": "9208ff4a08dcb674ce2df132399a5aa3ddfac21c", "astute_sha": "d96a80b63198a578b2c159edbd76048819039eb0", "feature_groups": ["experimental"], "release": "6.1", "fuelmain_sha": "9bdbd5018ed8fb6ff8af5fadadc49969d7e58a13", "fuellib_sha": "7d1e708297bd8fb4619210779f93d00201c95bba"}}}, "auth_required": true, "api": "1.0", "nailgun_sha": "0435d55f252796e77791c62405af8f341338ae73", "openstack_version": "2014.2-6.1", "production": "docker", "python-fuelclient_sha": "9208ff4a08dcb674ce2df132399a5aa3ddfac21c", "astute_sha": "d96a80b63198a578b2c159edbd76048819039eb0", "feature_groups": ["experimental"], "release": "6.1", "fuelmain_sha": "9bdbd5018ed8fb6ff8af5fadadc49969d7e58a13", "fuellib_sha": "7d1e708297bd8fb4619210779f93d00201c95bba"}