A second attempt to create the 'round one' doubled images in the Montage campaign (recurring bug)

[CiellB]

Steps to reproduce:

• Take a new Montage campaign
• Create round 1 with jury members and quorum 3
• Activate round 1
• Delete this round 1
• Create a second round 1 with jury members and quorum 3
• Activate this second round 1
• Montage pulls in all images for the second time? = double the amount of images in the campaign?, so jury members get assigned a double number a tasks.

Example from today in campaign #942: I have no option to correct this, so they are now starting new with a fresh Montage campaign.
I was able to replicate this in the beta.

[lgelauff]

There's still a Todo in add_entries in rdb.py:

> # TODO: you shouldn't be able to use this method to add
>         # entries to anything other than the first round in a campaign

Could that be related?