Cluster verify: factor out error codes and functions
Cluster verify: factor out error codes and functions

We move all error code definitions, plus the _Error and _ErrorIf helpers,
to a private _VerifyErrors mix-in class that can be later shared by the new
two cluster verify LUs.

(_Error and _ErrorIf code was moved around verbatim, except to disable
"_VerifyError class does not have 'op' or '_feedback_fn' members" errors
from pylint.)

Signed-off-by: Adeodato Simo <16293852a0900193fe70fa7d24f714f37ba99a56@google.com>
Signed-off-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

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