tests: removing intg/ts_cache.py

the following test cases are now covered in system/test_cache.py and
this can be removed.

* fixed assertion writes_to_both_databases tests
* added test detecting modification and deletion for groups
** test is a common user story and functional, changed priority to
critical
* added "integration" test invalidating user, group, netgroup objects

src/tests/intg/Makefile.am

@@ -19,7 +19,6 @@ dist_noinst_DATA = \
     test_ldap.py \
     test_memory_cache.py \
     test_session_recording.py \
-    test_ts_cache.py \
     test_netgroup.py \
     test_sssctl.py \
     files_ops.py \