create_server fails if server is not unique

The error message for the exception is:
(IntegrityError) UNIQUE constrait failed: table.column ....
The fix is to add the string "unique constraint failed" when looking
for IntegrityErrors to convert to exceptions.Duplicates.
Closes-Bug: 1290560
Change-Id: Id8e28443cf238a888e780f38f983129e5ac1d2f0
Merge "create_server fails if server is not unique"