qerror: add proper ErrorClass value for QERR_ macros

qerror: add proper ErrorClass value for QERR_ macros

This commit replaces the place holder value for the ErrorClass
argument with a proper ErrorClass value for all QERR_ macros.

All current errors are mapped to GenericError, except for errors
CommandNotFound, DeviceEncrypted, DeviceNotActive, DeviceNotFound,
KVMMissingCap and MigrationExpected, which are maintained as they
are today.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>