Fix Bug 1781 RO does not create management networks where appropriate

If there is mgmt-network in the descriptor,
there is no mapping of that network to a VIM network in the descriptor,
also there is no mapping in the "--config" parameter or at VIM creation;
that mgmt-network will be created.

Change-Id: Ic3ba8bed0417c49bf7d205b91c04703c6aa1b6a3
Signed-off-by: aticig <gulsum.atici@canonical.com>