query: Improve error checking
query: Improve error checking

- Show only field definition, not callback when a result row is
  inconsistent
- Show list of duplicate titles if there are any (module load time)

Signed-off-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>
Reviewed-by: Adeodato Simo <16293852a0900193fe70fa7d24f714f37ba99a56@google.com>

dimara/ganeti,mbakke/ganeti,leshchevds/ganeti,bitemyapp/ganeti,apyrgio/ganeti,ganeti/ganeti,ganeti-github-testing/ganeti-test-1,grnet/snf-ganeti,dimara/ganeti,apyrgio/ganeti,apyrgio/snf-ganeti,ganeti/ganeti,apyrgio/snf-ganeti,yiannist/ganeti,andir/ganeti,onponomarev/ganeti,grnet/snf-ganeti,mbakke/ganeti,bitemyapp/ganeti,onponomarev/ganeti,ganeti/ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,andir/ganeti,yiannist/ganeti,leshchevds/ganeti,leshchevds/ganeti,mbakke/ganeti