Fix list_group_snapshots API in v3 group_snapshots_client

The API (list group snapshots with details) is wrongly implemented now.
It uses the '?detail=True' to get group snapshots list with details,
which only returns 'id' and 'name' elements of group snapshots.

This patch fixes on group snapshots api and according api/unit tests to
solve this problem.

Closes-bug: #1715786
Change-Id: Ia869a7dc9654a6253c2209724afd2fe2f8519558
diff --git a/releasenotes/notes/fix-list-group-snapshots-api-969d9321002c566c.yaml b/releasenotes/notes/fix-list-group-snapshots-api-969d9321002c566c.yaml
new file mode 100644
index 0000000..775a383
--- /dev/null
+++ b/releasenotes/notes/fix-list-group-snapshots-api-969d9321002c566c.yaml
@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fix list_group_snapshots API in v3 group_snapshots_client: Bug#1715786.
+    The url path for list group snapshots with details API is changed from
+    ``?detail=True`` to ``/detail``.