Support a many-to-many CMS site to SE relation

Make sure that data is read properly from siteDB when building
lists of sites from a SE, taking into account that a se can be
shared by many CMS sites.

Update the test emulator such that the unit test works when
disabling the emulator in it.
Merge pull request #4576 from dballesteros7/multipleSE-insertion

Support a many-to-many CMS site to SE relation