Related-Bug: #1390392

1. Updated menu.xml such that relevant menus will be shown in case of vCenter & vCenter + OpenStack
2. Hide CPU/Memory for Instances in case of vCenter mode
3. Enable Monitor > Infrastructure,Configure > Infrastructure menu in case of only vcenter
   orchestration mode
4. Show only one subnet while creating network in case of vCenter

Change-Id: I9eaf640184dbb63469bc873c7a1d872c93375991