bmcweb: Fix some errors in Redfish Sessions

Two errors were identified in the Redfish sessions implementation.

1. All user "roles" return a description containing Adminstrator,
instead of containing the name of the role.
2. The SessionService implementation was missing the link to sessions
collection.

These are resolved in this commit.

Tested By:
Ran service validator, no errors.

Change-Id: Ib48ab1756d78724b4bab124c8cf135c8a61d94a6
Signed-off-by: Ed Tanous <ed.tanous@intel.com>
diff --git a/redfish-core/lib/redfish_sessions.hpp b/redfish-core/lib/redfish_sessions.hpp
index addb287..59805a0 100644
--- a/redfish-core/lib/redfish_sessions.hpp
+++ b/redfish-core/lib/redfish_sessions.hpp
@@ -235,6 +235,9 @@
                 .getTimeoutInSeconds();
         res.jsonValue["ServiceEnabled"] = true;
 
+        res.jsonValue["Sessions"] = {
+            {"@odata.id", "/redfish/v1/SessionService/Sessions"}};
+
         res.end();
     }
 };