handle bad SemVer for CRD creation

[ukclivecox]

For GKE the version returned by cc.discoveryClient.ServerVersion() can be of the form 1.20+ which does not parse normal semantic version check we use in Operator resulting in semver.NewConstraint(">= 1.18.0") returning false.

See

seldon-core/operator/utils/k8s/crd.go

Lines 105 to 117 in a9e3793

	sv, err := cc.discoveryClient.ServerVersion()
	if err != nil {
	return nil, err
	}
	v, err := semver.NewVersion(sv.String())
	if err != nil {
	return nil, err
	}
	c, err := semver.NewConstraint(">= 1.18.0")
	if err != nil {
	return nil, err
	}
	check := c.Check(v)