builder/openstack/step_create_image.go: pass context for cancellation
builder/openstack/step_create_image.go: pass context for cancellation

fix #7325

tas50/packer,timsutton/packer,tas50/packer,timsutton/packer,bryson/packer,hashicorp/packer,timsutton/packer,hashicorp/packer,tas50/packer,tas50/packer,rnaveiras/packer,grubernaut/packer,ricardclau/packer,mitchellh/packer,dave2/packer,bryson/packer,paulmey/packer,rnaveiras/packer,ricardclau/packer,mitchellh/packer,dave2/packer,hashicorp/packer,grubernaut/packer,grubernaut/packer,pecigonzalo/packer,dave2/packer,pecigonzalo/packer,dave2/packer,ricardclau/packer,paulmey/packer,paulmey/packer,dave2/packer,paulmey/packer,grubernaut/packer,paulmey/packer,dave2/packer,mitchellh/packer,rnaveiras/packer,rnaveiras/packer,bryson/packer,grubernaut/packer,mitchellh/packer,grubernaut/packer,tas50/packer,paulmey/packer,tas50/packer,bryson/packer,ricardclau/packer,timsutton/packer,timsutton/packer,ricardclau/packer,bryson/packer,bryson/packer,rnaveiras/packer,pecigonzalo/packer,rnaveiras/packer,pecigonzalo/packer,timsutton/packer,mitchellh/packer,hashicorp/packer,ricardclau/packer