CIMI Systems: fixed id not being set for SystemSystemCollection.
This was missed in the patch for DTACLOUD-559
(commit 640405627827bdf0d38e3418647d2d36fd272d74)
Also, applied name change of add_/remove_ methods to collections.

    https://issues.apache.org/jira/browse/DTACLOUD-559
    https://github.com/deltacloud/deltacloud-core/pull/28
    https://github.com/deltacloud/deltacloud-core/pull/27