Filter out only used users in mam_helper:serv_users/1

[arcusfelis]

So, we don't call remove_user if not needed

Proposed changes include:

• it does not call remove_user for non-existing test users.
• Should be a bit faster to execute tests in mam_SUITE too.

This user gets filtered out, for example:

    {astrid, [
        {username, <<"astrid">>},
        {server, <<"sogndal">>},
        {host, <<"localhost">>},
        {password, <<"doctor">>}]},

[mongoose-im]

small_tests_24 / small_tests / 0bcc208
Reports root / small

---

internal_mnesia_24 / internal_mnesia / 0bcc208
Reports root/ big
OK: 1588 / Failed: 0 / User-skipped: 288 / Auto-skipped: 0

---

dynamic_domains_24 / pgsql_mnesia / 0bcc208
Reports root/ big
OK: 1684 / Failed: 0 / User-skipped: 114 / Auto-skipped: 0

---

small_tests_22 / small_tests / 0bcc208
Reports root / small

---

dynamic_domains_23 / pgsql_mnesia / 0bcc208
Reports root/ big
OK: 1684 / Failed: 0 / User-skipped: 114 / Auto-skipped: 0

---

small_tests_23 / small_tests / 0bcc208
Reports root / small

---

ldap_mnesia_24 / ldap_mnesia / 0bcc208
Reports root/ big
OK: 1515 / Failed: 0 / User-skipped: 361 / Auto-skipped: 0

---

ldap_mnesia_22 / ldap_mnesia / 0bcc208
Reports root/ big
OK: 1515 / Failed: 0 / User-skipped: 361 / Auto-skipped: 0

---

ldap_mnesia_23 / ldap_mnesia / 0bcc208
Reports root/ big
OK: 1515 / Failed: 0 / User-skipped: 361 / Auto-skipped: 0

---

elasticsearch_and_cassandra_24 / elasticsearch_and_cassandra_mnesia / 0bcc208
Reports root/ big
OK: 1891 / Failed: 0 / User-skipped: 284 / Auto-skipped: 0

---

pgsql_mnesia_24 / pgsql_mnesia / 0bcc208
Reports root/ big
OK: 3087 / Failed: 1 / User-skipped: 184 / Auto-skipped: 0

service_domain_db_SUITE:db:db_keeps_syncing_after_cluster_join

{error,{test_case_failed,{[<<"example1.com">>,<<"example2.com">>,
               <<"example3.com">>],
              [<<"example1.com">>,<<"example2.com">>,
               <<"example3.com">>,<<"example4.com">>]}}}

Report log

---

pgsql_mnesia_22 / pgsql_mnesia / 0bcc208
Reports root/ big
OK: 3088 / Failed: 0 / User-skipped: 184 / Auto-skipped: 0

---

mysql_redis_24 / mysql_redis / 0bcc208
Reports root/ big
OK: 3071 / Failed: 0 / User-skipped: 201 / Auto-skipped: 0

---

pgsql_mnesia_23 / pgsql_mnesia / 0bcc208
Reports root/ big
OK: 3088 / Failed: 0 / User-skipped: 184 / Auto-skipped: 0

---

mssql_mnesia_24 / odbc_mssql_mnesia / 0bcc208
Reports root/ big
OK: 3088 / Failed: 0 / User-skipped: 184 / Auto-skipped: 0

---

riak_mnesia_24 / riak_mnesia / 0bcc208
Reports root/ big
OK: 1738 / Failed: 0 / User-skipped: 287 / Auto-skipped: 0

---

pgsql_mnesia_24 / pgsql_mnesia / 0bcc208
Reports root/ big
OK: 3088 / Failed: 0 / User-skipped: 184 / Auto-skipped: 0

[codecov]

Codecov Report

Merging #3230 (0bcc208) into master (413e706) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3230      +/-   ##
==========================================
- Coverage   80.30%   80.26%   -0.04%     
==========================================
  Files         398      398              
  Lines       32524    32524              
==========================================
- Hits        26117    26105      -12     
- Misses       6407     6419      +12     

Impacted Files	Coverage Δ
src/elasticsearch/mongoose_elasticsearch.erl	76.92% <0.00%> (-7.70%)	⬇️
src/mam/mod_mam_elasticsearch_arch.erl	85.08% <0.00%> (-1.76%)	⬇️
src/ejabberd_s2s_out.erl	60.82% <0.00%> (-1.60%)	⬇️
src/mod_muc_room.erl	76.94% <0.00%> (-0.24%)	⬇️
src/mod_muc_log.erl	77.88% <0.00%> (ø)
src/ejabberd_c2s.erl	89.28% <0.00%> (+0.07%)	⬆️
src/global_distrib/mod_global_distrib_utils.erl	65.42% <0.00%> (+0.93%)	⬆️

---

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