Description of problem:
This error is pointless and confuses the customers (sfdc#00978965, for instance).
It should be debug or info in this flow.
Or the flow is wrong.
Please see the details below:

Consider the log messages of DomainMonitorThread flow:
Thread-21::DEBUG::2013-11-18 22:37:22,793::domainMonitor::178::Storage.DomainMonitorThread::(_monitorDomain) Refreshing domain 534432b5-c19b-4181-9764-aee420a931f6
Thread-21::ERROR::2013-11-18 22:37:22,794::sdc::137::Storage.StorageDomainCache::(_findDomain) looking for unfetched domain 534432b5-c19b-4181-9764-aee420a931f6
Thread-21::ERROR::2013-11-18 22:37:22,794::sdc::153::Storage.StorageDomainCache::(_findUnfetchedDomain) looking for domain 534432b5-c19b-4181-9764-aee420a931f6
--
Thread-21::DEBUG::2013-11-18 22:42:24,017::domainMonitor::178::Storage.DomainMonitorThread::(_monitorDomain) Refreshing domain 534432b5-c19b-4181-9764-aee420a931f6
Thread-21::ERROR::2013-11-18 22:42:24,018::sdc::137::Storage.StorageDomainCache::(_findDomain) looking for unfetched domain 534432b5-c19b-4181-9764-aee420a931f6
Thread-21::ERROR::2013-11-18 22:42:24,018::sdc::153::Storage.StorageDomainCache::(_findUnfetchedDomain) looking for domain 534432b5-c19b-4181-9764-aee420a931f6
--
Thread-21::DEBUG::2013-11-18 22:47:25,353::domainMonitor::178::Storage.DomainMonitorThread::(_monitorDomain) Refreshing domain 534432b5-c19b-4181-9764-aee420a931f6
Thread-21::ERROR::2013-11-18 22:47:25,354::sdc::137::Storage.StorageDomainCache::(_findDomain) looking for unfetched domain 534432b5-c19b-4181-9764-aee420a931f6
Thread-21::ERROR::2013-11-18 22:47:25,360::sdc::153::Storage.StorageDomainCache::(_findUnfetchedDomain) looking for domain 534432b5-c19b-4181-9764-aee420a931f6
--

Every 5 minutes (repo_stats_cache_refresh_timeout) monitorDomain would call 
  sdCache.manuallyRemoveDomain(self.sdUUID)
which would remove currently monitored domain from the cache.
Next, it will perform produce on the same domain, which will in turn go to sdCache and call: realProduce -> _findDomain.
In _findDomain it will try to access knownSDs list, but since this SD was just removed from the cache, it would not be present in this list.
This will print the first ERROR message:
     def _findDomain(self, sdUUID):
        try:
            findMethod = self.knownSDs[sdUUID]
        except KeyError:
            self.log.error("looking for unfetched domain %s", sdUUID)
            findMethod = self._findUnfetchedDomain                                                       
And then _findUnfetchedDomain will print the second error message:
    def _findUnfetchedDomain(self, sdUUID):
        import blockSD
        import localFsSD                                                                                 
        import nfsSD
                                                                                                         
        self.log.error("looking for domain %s", sdUUID)
--------------------------------------------------------------


Version-Release number of selected component (if applicable):
checked life on vdsm-4.10.2-27.0.el6ev.x86_64.
From 3.3 code(4.13.0-0.8.beta1.el6ev.x86_64), sdc code didn't change, so I believe the same would happen on 3.3.

How reproducible:
100%

Steps to Reproduce:
1. Get a running setup with Master Data Storage Domain.
2. Check /var/log/vdsm/vdsm/log for the error "looking for unfetched domain" with a command similar to this:
# grep -A2 'Refreshing domain 534432b5-c19b-4181-9764-aee420a931f6' /var/log/vdsm/vdsm.log

Actual results:
Will print the messages from the beginning of the description.

Expected results:
Should not print those messages as ERRORs.