Support additional config keys for Swift

[nightfury1204]

When I deployed Vault in Kubernetes with Swift backend storage (OVH provider). I was kept getting this error: Error initializing storage of type swift: Unable to access container "vault": Container Not Found.

Reason was vault can not find the storage which isn't in default region (for this case WAW1).

This problem can be solved by providing Region.

github.com/ncw/swift library supports additional keys when creating a swift connection. Some of these keys are needed with various cloud providers. Can these additional keys be supported?

Region:
TenantId:
TrustId:
StorageUrl:
AuthToken:

Restic also uses the same library for swift https://github.com/restic/restic/blob/master/internal/backend/swift/swift.go#L45