Removed duplicate of '/v1' in uri on topic subscribing and unsubcribing

[almliden]

Fixing duplicate of /v1in URI when subscribing/unsubscribing to a topic.

When configuring AGConnectApp with ApiBaseUri the default value of the URI already contains /v1, and since it was present in the URI:s methods SubscribeToTopicAsync and UnsubscribeFromTopicAsync we were left with duplicates which points us to the wrong resource, eg [...]/v1/v1/[ClientId]/subscribe:topic.

This fix removes the duplicate of /v1 to point us to the correct resource.