Test cache and async code

[NelsonVides]

This PR adds a suite to cover the parts of cache and async workers code that wasn't covered and was only previously fixed ad-hoc in #3508 and #3518.

[codecov]

Codecov Report

Merging #3529 (82ae390) into master (cc4c859) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3529      +/-   ##
==========================================
+ Coverage   81.06%   81.08%   +0.01%     
==========================================
  Files         419      419              
  Lines       32297    32298       +1     
==========================================
+ Hits        26183    26190       +7     
+ Misses       6114     6108       -6     

Impacted Files	Coverage Δ
src/mongoose_batch_worker.erl	60.00% <100.00%> (-3.64%)	⬇️
src/mod_roster.erl	78.52% <0.00%> (-0.48%)	⬇️
src/pubsub/mod_pubsub.erl	73.31% <0.00%> (-0.18%)	⬇️
src/mod_muc_log.erl	78.11% <0.00%> (ø)
src/pubsub/mod_pubsub_db_mnesia.erl	92.85% <0.00%> (+0.42%)	⬆️
src/domain/mongoose_domain_loader.erl	90.17% <0.00%> (+0.89%)	⬆️
src/logger/mongoose_log_filter.erl	79.45% <0.00%> (+1.36%)	⬆️
src/cassandra/mongoose_cassandra_worker.erl	68.54% <0.00%> (+2.81%)	⬆️
src/cassandra/mongoose_cassandra.erl	81.48% <0.00%> (+3.70%)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update cc4c859...82ae390. Read the comment docs.

[mongoose-im]

small_tests_24 / small_tests / 82ae390
Reports root / small

---

small_tests_23 / small_tests / 82ae390
Reports root / small

---

dynamic_domains_pgsql_mnesia_23 / pgsql_mnesia / 82ae390
Reports root/ big
OK: 2691 / Failed: 0 / User-skipped: 238 / Auto-skipped: 0

---

dynamic_domains_mysql_redis_24 / mysql_redis / 82ae390
Reports root/ big
OK: 2674 / Failed: 0 / User-skipped: 255 / Auto-skipped: 0

---

dynamic_domains_pgsql_mnesia_24 / pgsql_mnesia / 82ae390
Reports root/ big
OK: 2691 / Failed: 0 / User-skipped: 238 / Auto-skipped: 0

---

dynamic_domains_mssql_mnesia_24 / odbc_mssql_mnesia / 82ae390
Reports root/ big
OK: 2691 / Failed: 0 / User-skipped: 238 / Auto-skipped: 0

---

ldap_mnesia_23 / ldap_mnesia / 82ae390
Reports root/ big
OK: 1500 / Failed: 0 / User-skipped: 390 / Auto-skipped: 0

---

ldap_mnesia_24 / ldap_mnesia / 82ae390
Reports root/ big
OK: 1500 / Failed: 0 / User-skipped: 390 / Auto-skipped: 0

---

internal_mnesia_24 / internal_mnesia / 82ae390
Reports root/ big
OK: 1541 / Failed: 0 / User-skipped: 349 / Auto-skipped: 0

---

pgsql_mnesia_23 / pgsql_mnesia / 82ae390
Reports root/ big
OK: 3078 / Failed: 0 / User-skipped: 247 / Auto-skipped: 0

---

pgsql_mnesia_24 / pgsql_mnesia / 82ae390
Reports root/ big
OK: 3078 / Failed: 0 / User-skipped: 247 / Auto-skipped: 0

---

mysql_redis_24 / mysql_redis / 82ae390
Reports root/ big
OK: 3073 / Failed: 0 / User-skipped: 252 / Auto-skipped: 0

---

elasticsearch_and_cassandra_24 / elasticsearch_and_cassandra_mnesia / 82ae390
Reports root/ big
OK: 1834 / Failed: 0 / User-skipped: 363 / Auto-skipped: 0

---

mssql_mnesia_24 / odbc_mssql_mnesia / 82ae390
Reports root/ big
OK: 3078 / Failed: 0 / User-skipped: 247 / Auto-skipped: 0

---

riak_mnesia_24 / riak_mnesia / 82ae390
Reports root/ big
OK: 1680 / Failed: 0 / User-skipped: 363 / Auto-skipped: 0

[Premwoik]

Looks good to me :)