queries to kv1 should return path variable not string (#85)

Currently if the API is determined to be kv1 the path is always set to
path, whereas it should be set to the value of the variable passed in.

Closes #78

pkg/vaultengine/vaultclient.go

@@ -47,7 +47,7 @@ func (client *Client) MountpathSplitPrefix(path string) (string, string, error)
 	if err != nil {
 		// any 404 indicates k/v v1
 		if resp != nil && resp.StatusCode == 404 {
-			return "", "path", nil
+			return "", path, nil
 		}
 		return "", "", err
 	}