Revert "Fix a potential issue in ioucon."

This reverts commit 08cb3de6837c11074dfdc11a8cba74410be48fe5.
Send error if L1 keepalive messages are not supported.
Fix console port restoration for IOU and VPCS (when loading a project).
Forbid additional properties in schemas, add missing ones.
Use SIGBREAK to stop VPCS on Windows.
Bump version to alpha5.
Bump to version 1.0a6.dev1
Fixes VPCS start on Linux/UNIX. Fixes #15.
Fixes validation issue with c2600 XM chassis.
Fixes privileged access checks for IOU.
Bump to version 1.0a6.dev2