Add Neutron support

Currently create instance doesnt work in OS installation with Neutron.
To get it work, additional parameter 'nics' should be specified
in Nova 'create' call.
This change allows user to pass 'nics' parameter when create instance.

Syntax to specify '--nic' parameter is same as in novaclient.
--nic <net-id=net-uuid,v4-fixed-ip=ip-addr,port-id=port-uuid>
This parameter can be specified multiple times, to attach multiple
network interfaces to instance.

Closes-Bug: #1257838

Change-Id: I76fb0d99512b1ee70441c924835a900ba0b7acd1
Fixes troveclient raising undefined exception ConnectionError

Reason: ConnectionError exception is raised which is not defined in
        python-troveclient/troveclient/openstack/common/apiclient/exceptions.py

Change: ConnectionError should be renamed to ConnectionRefused.

Closes-Bug: #1240950

Change-Id: I73219d29efd71185cdf6ff56a7fe41165541681f
Merge "Add Neutron support"