Basic pluto with IKEv2 on the initiator (west), and on the responder.

This test enables --impair-major-version-bump that will send a higher
major version number on the responder. The connection should fail.

See: https://tools.ietf.org/html/rfc5996#section-2.5

The major version number should be incremented only if the packet
formats or required actions have changed so dramatically that an
older version node would not be able to interoperate with a newer
version node if it simply ignored the fields it did not understand
and took the actions specified in the older specification.  The minor
version number indicates new capabilities, and MUST be ignored by a
node with a smaller minor version number, but used for informational
purposes by the node with the larger minor version number.  For
example, it might indicate the ability to process a newly defined
Notify message type.  The node with the larger minor version number
would simply note that its correspondent would not be able to
understand that message and therefore would not send it.



