Description of problem:

After the memcache expired, a group will be missing in subsequence query


Version-Release number of selected component (if applicable):
sssd-1.16.4-35.el7.x86_64

How reproducible:
Always


Steps to Reproduce:
0. Install ipa-server-trust-ad and execute ipa-adtrust-install

1. Make users/groups as follows.
  ipa user-add ad_user --first foo --last bar --gid 11111
  ipa group-add ad_group
  ipa group-add-member ad_group --users=ad_user

  ipa group-add ex_user  --external
  ipa group-add ex_group --external
  ipa group-add-member ex_user  --users=ad_user
  ipa group-add-member ex_group --external=ad_group --groups=ad_group

  ipa group-add group_a
  ipa group-add group_b
  ipa group-add-member group_a --groups=ex_user --groups=ex_group
  ipa group-add-member group_b --groups=ex_user --groups=ex_group

2. Disable the memcache_timeout
   This is to make the bug occur faster.

   Either:
    a. Set "memcache_timeout = 0" in sssd.conf 
    b. export SSS_NSS_USE_MEMCACHE=NO

3. Clear sssd cache and restart
 # systemctl stop sssd ; rm -rf /var/lib/sss/{mc,db}/* ; systemctl start sssd

4. i=0; while : ; do date; strace -o /tmp/id_ad_user.$i id ad_user ; sleep 2 ; : $((i++)); done

Actual results:
  One group (group_b) is missing:

  [...date..]
  uid=180600025(ad_user) gid=11111 groups=11111,180600027(group_a),180600028(group_b),180600026(ad_group)
  [..another date..]
  uid=180600025(ad_user) gid=11111 groups=11111,180600026(ad_group),180600027(group_a)


Expected results:
  All group should be there:

  [...date..]
  uid=180600025(ad_user) gid=11111 groups=11111,180600027(group_a),180600028(group_b),180600026(ad_group)
  [..another date..]
  uid=180600025(ad_user) gid=11111 groups=11111,180600027(group_a),180600028(group_b),180600026(ad_group)


Additional info:
1. Setting longer memcache_timeout will mitigate the problem, but that is not desirable because 
      it does not reflect the user or group modification.

2. A user mentioned that:
   The bug can be reproduced between:
     RHEL7.3 ~ RHEL7.8 beta

   But working fine with 
     RHEL7.2, RHEL8.2 alpha