dovetail: conditional steps to run against specific scenarios

dovetail: conditional steps to run against specific scenarios

JIRA: DOVETAIL-432

1, the community CI resource is limited, for dovetail CI job,
there's no need to run against all scenarios, by now,
nosdn-nofeature-ha odl_l2-bgpvpn-ha odl_l2-nofeature-ha is enough.
2, jenkins conditional plugin will be used.
   plugin should be installed
   https://wiki.jenkins-ci.org/display/JENKINS/Conditional+BuildStep+Plugin
3, take compass as an example to see if it works

Change-Id: Ib23835cbf8801c36e35e088cd0d8bf2d6380e81a
Signed-off-by: MatthewLi <matthew.lijun@huawei.com>