CP-28546: Remove 4.0 from supported_api_versions
CP-28546: Remove 4.0 from supported_api_versions

Currently we do not support 4.0 because we are not compatible with the
old return type of Datapath.attach.

We need to decide what to do with the tapdisk datapath plugin - we can
either update to to v5, or add a compat layer here and make
xapi-storage-script compatible with v4.

Signed-off-by: Gabor Igloi <7535f5501fd71876c93d896691e178fd3a11cfbb@citrix.com>

xapi-project/message-switch,xapi-project/message-switch,xapi-project/message-switch