VMM/serviceset: Fixed a conditional ProgrammingError. Affects only setups with Dovecot < v1.2.beta2. Actually the SQL query in method ServiceSet._load_by_services wasn't updated. Removed unnecessary code, which would have also produced a ProgrammingError, if it would have been correct.

[install]
compile = 1
optimize = 1

[sdist]
formats = bztar