Upgrade mitchellh/hashstructure

[dnephin]

https://github.com/mitchellh/hashstructure released a V2 which fixes (mitchellh/hashstructure#18, mitchellh/hashstructure#20). If we don't persist the hashes anywhere it should be safe to upgrade. It sounds like there is a way to get the old V1 hashes if we do persist them somewhere.

Current usage:

agent/agent_endpoint.go:			rawHash, err := hashstructure.Hash(reply, nil)
agent/cache-types/connect_ca_leaf.go:	v, err := hashstructure.Hash([]interface{}{
agent/cache-types/service_checks.go:	v, err := hashstructure.Hash([]interface{}{
agent/cache-types/service_checks.go:	b, err := hashstructure.Hash(wrapper, nil)
agent/consul/discoverychain/compile.go:		v, err := hashstructure.Hash(customization, nil)
agent/structs/config_entry.go:	v, err := hashstructure.Hash([]interface{}{
agent/structs/config_entry.go:	v, err := hashstructure.Hash(struct {
agent/structs/config_entry_discoverychain.go:	v, err := hashstructure.Hash(struct {
agent/structs/intention.go:	v, err := hashstructure.Hash(q.Match, nil)
agent/structs/prepared_query.go:	v, err := hashstructure.Hash([]interface{}{
agent/structs/structs.go:	v, err := hashstructure.Hash([]interface{}{
agent/structs/structs.go:	v, err := hashstructure.Hash([]interface{}{
agent/structs/structs.go:	v, err := hashstructure.Hash([]interface{}{
agent/structs/structs.go:	v, err := hashstructure.Hash([]interface{}{