[OS] fix restore tests

[NelsonVides]

Here we're not saving the config properly after tests are ran, so the restore at the end_per_group didn't restore anything.

[chrzaszcz]

Looks good 👍

[codecov]

Codecov Report

Merging #3592 (460a5e8) into master (6fe50c3) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3592      +/-   ##
==========================================
- Coverage   80.88%   80.85%   -0.03%     
==========================================
  Files         426      426              
  Lines       32386    32386              
==========================================
- Hits        26194    26187       -7     
- Misses       6192     6199       +7     

Impacted Files	Coverage Δ
src/cassandra/mongoose_cassandra.erl	77.77% <0.00%> (-3.71%)	⬇️
...rc/smart_markers/mod_smart_markers_rdbms_async.erl	88.88% <0.00%> (-3.71%)	⬇️
src/mam/mod_mam_muc_rdbms_arch_async.erl	82.85% <0.00%> (-2.86%)	⬇️
src/cassandra/mongoose_cassandra_worker.erl	65.72% <0.00%> (-2.82%)	⬇️
src/muc_light/mod_muc_light.erl	84.75% <0.00%> (-0.75%)	⬇️
src/mod_roster.erl	78.52% <0.00%> (-0.24%)	⬇️
src/mod_muc_room.erl	76.70% <0.00%> (-0.18%)	⬇️
src/pubsub/mod_pubsub.erl	73.31% <0.00%> (+0.11%)	⬆️
src/mam/mod_mam_meta.erl	97.40% <0.00%> (+1.29%)	⬆️
src/mam/mod_mam_elasticsearch_arch.erl	86.84% <0.00%> (+1.75%)	⬆️
... and 2 more

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[mongoose-im]

small_tests_24 / small_tests / 460a5e8
Reports root / small

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small_tests_23 / small_tests / 460a5e8
Reports root / small

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dynamic_domains_pgsql_mnesia_24 / pgsql_mnesia / 460a5e8
Reports root/ big
OK: 2822 / Failed: 0 / User-skipped: 133 / Auto-skipped: 0

---

dynamic_domains_mysql_redis_24 / mysql_redis / 460a5e8
Reports root/ big
OK: 2805 / Failed: 0 / User-skipped: 150 / Auto-skipped: 0

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dynamic_domains_pgsql_mnesia_23 / pgsql_mnesia / 460a5e8
Reports root/ big
OK: 2822 / Failed: 0 / User-skipped: 133 / Auto-skipped: 0

---

dynamic_domains_mssql_mnesia_24 / odbc_mssql_mnesia / 460a5e8
Reports root/ big
OK: 2822 / Failed: 0 / User-skipped: 133 / Auto-skipped: 0

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ldap_mnesia_23 / ldap_mnesia / 460a5e8
Reports root/ big
OK: 1505 / Failed: 0 / User-skipped: 399 / Auto-skipped: 0

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ldap_mnesia_24 / ldap_mnesia / 460a5e8
Reports root/ big
OK: 1505 / Failed: 0 / User-skipped: 399 / Auto-skipped: 0

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internal_mnesia_24 / internal_mnesia / 460a5e8
Reports root/ big
OK: 1546 / Failed: 0 / User-skipped: 358 / Auto-skipped: 0

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pgsql_mnesia_24 / pgsql_mnesia / 460a5e8
Reports root/ big
OK: 3196 / Failed: 0 / User-skipped: 142 / Auto-skipped: 0

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elasticsearch_and_cassandra_24 / elasticsearch_and_cassandra_mnesia / 460a5e8
Reports root/ big
OK: 1853 / Failed: 0 / User-skipped: 366 / Auto-skipped: 0

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pgsql_mnesia_23 / pgsql_mnesia / 460a5e8
Reports root/ big
OK: 3196 / Failed: 0 / User-skipped: 142 / Auto-skipped: 0

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mssql_mnesia_24 / odbc_mssql_mnesia / 460a5e8
Reports root/ big
OK: 3196 / Failed: 0 / User-skipped: 142 / Auto-skipped: 0

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riak_mnesia_24 / riak_mnesia / 460a5e8
Reports root/ big
OK: 1696 / Failed: 0 / User-skipped: 365 / Auto-skipped: 0