Fix regression in PAM groups handling

Commit 991770cc5d re-introduced
a problem which was earler fixed in
4183d8ddbf. This commit fixes the
regression so that pam_group.so on Linux now works again.

(cherry picked from commit c2b3cc6fc27c8c354ec39eac016cceb05430370d)

sesman/sesexec/session.c

@@ -680,6 +680,19 @@ session_start_wrapped(struct login_info *login_info,
     int window_manager_pid;
     enum scp_screate_status status = E_SCP_SCREATE_GENERAL_ERROR;
 
+    /* Set the secondary groups before starting the session to prevent
+     * problems on PAM-based systems (see Linux pam_setcred(3)).
+     * If we have *BSD setusercontext() this is not done here */
+#ifndef HAVE_SETUSERCONTEXT
+    if (g_initgroups(login_info->username) != 0)
+    {
+        LOG(LOG_LEVEL_ERROR,
+            "Failed to initialise secondary groups for %s: %s",
+            login_info->username, g_get_strerror());
+        return E_SCP_SCREATE_GENERAL_ERROR;
+    }
+#endif
+
     if (auth_start_session(login_info->auth_info, s->display) != 0)
     {
         // Errors are logged by the auth module, as they are
@@ -706,19 +719,6 @@ session_start_wrapped(struct login_info *login_info,
     }
 #endif
 
-    /* Set the secondary groups before starting the session to prevent
-     * problems on PAM-based systems (see Linux pam_setcred(3)).
-     * If we have *BSD setusercontext() this is not done here */
-#ifndef HAVE_SETUSERCONTEXT
-    if (g_initgroups(login_info->username) != 0)
-    {
-        LOG(LOG_LEVEL_ERROR,
-            "Failed to initialise secondary groups for %s: %s",
-            login_info->username, g_get_strerror());
-        return E_SCP_SCREATE_GENERAL_ERROR;
-    }
-#endif
-
     /* start the X server in a new process group.
      *
      * We group the X server, window manager and chansrv in a single