[Server Manager: sources.list for ubuntu points to repos in de.ubuntu.com]

Closes-Bug: #1402045

Issue:
Since the sources.list populated by smgr points to de.ubuntu.com.
We have seen it to be slow.

Fix:
Changed refs to de.ubuntu.com to ubuntu.com

Testing:
Issue re-image and see that it goes through with correct sources.list
populated.

Change-Id: I711226a7e12f56c9266bc05a5a50ae677f52d4cf
Merge "[Server Manager: sources.list for ubuntu points to repos in de.ubuntu.com]" into R2.0