core: Initialize internal lists in IscsiBond

Initialize the storage domains and the networks when fectching IscsiBond
from query command, also adding a test to the query.

Change-Id: I167b1c6d6c5f83022c18faad555c0ff2e6f1f44b
Bug-Url: https://bugzilla.redhat.com/1133279
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>
restapi:Fix CRUD operations for iSCSI Storage connection.

1) renaming class BackendIscsiBondStorageServerConnection to
BackendIscsiBondStorageConnectionResource to be compatible with the
plural resource name
2) Fix remove and get operations for Storage Connection in IscsiBond
3) Adding appropriate tests for resource commands in REST.

Usages:
Get a list of Storage Connections contained in the iSCSI bond:
Get
/api/datacenters/{datacenter_id}/iscsibonds/{iscsibond_id}/storageconnections/

Get a specific Storage Connection in the iSCSI bond:
Get
/api/datacenters/{datacenter_id}/iscsibonds/{iscsibond_id}/storageconnections/{storage_id}/

Adding a new Storage Connection to an existing iSCSI Bond:
POST /api/datacenters/{datacenter_id}/iscsibonds HTTP/1.1
Accept: application/xml
<storage_connection id="{connection_id}"></storage_connection>

Remove a Storage Connection from the existing iSCSi Bond:
DELETE /api/datacenters/{datacenter_id}/iscsibonds/{iscsibond_id}/storageconnections/{storage_id}/ HTTP/1.1

Change-Id: I2424067b4371b6a99f61ea687155c4082855aff5
Bug-Url: https://bugzilla.redhat.com/1133896
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>
core: Modify CDA message when adding connection to iSCSI bond

Modify a CDA message to also indicate the use case when user adds a
connection which already exists in the iSCSI bond.

Change-Id: Id66ef71008ed67901c388c82ec47d954e4ac60d7
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>