Prepare to release v0.12.1
Prepare to release v0.12.1

Signed-off-by: John Else <37b74501daa612e48fea94f9846ed4ddeb6a8f07@citrix.com>

djs55/xcp-idl,euanh/xcp-idl,xapi-project/message-switch,Chunjie/xcp-idl,xapi-project/message-switch,johnelse/xcp-idl,xapi-project/message-switch