Prevent infinite loop when domain isolation is on on both domains

[arcusfelis]

This PR addresses MIM-1395.

Proposed changes include:

• Fixes "Domain isolation causes an infinite loop".
• A test.

Description:
Step to reproduce:

Enable domain isolation for two domains, e.g.: `localhost`, `localhost.bis`

Send any message between the two domains, e.g. from `alice@localhost.bis` (A) to `bob@localhost` (B)

mod_domain_isolation handles message from A to B by sending an error reply from B to A, which in turn results in an error reply etc... error elements are accumulating forever in the packet (actually: until the hook timeout passes), eating memory and time.

Add test to domain_isolation_SUITE, fix the issue by not bouncing the error message back.

[codecov]

Codecov Report

Merging #3110 (9d531fe) into master (3d3ff8d) will increase coverage by 0.04%.
The diff coverage is 90.00%.

@@            Coverage Diff             @@
##           master    #3110      +/-   ##
==========================================
+ Coverage   79.18%   79.23%   +0.04%     
==========================================
  Files         387      387              
  Lines       31853    31861       +8     
==========================================
+ Hits        25224    25245      +21     
+ Misses       6629     6616      -13     

Impacted Files	Coverage Δ
src/mod_domain_isolation.erl	94.28% <90.00%> (-2.02%)	⬇️
...bal_distrib/mod_global_distrib_hosts_refresher.erl	71.69% <0.00%> (-1.89%)	⬇️
src/global_distrib/mod_global_distrib_utils.erl	65.09% <0.00%> (-0.95%)	⬇️
...c/global_distrib/mod_global_distrib_server_mgr.erl	76.83% <0.00%> (-0.57%)	⬇️
src/ejabberd_c2s.erl	89.13% <0.00%> (-0.08%)	⬇️
src/mod_muc_log.erl	77.72% <0.00%> (ø)
src/mod_roster.erl	76.79% <0.00%> (+0.23%)	⬆️
src/ejabberd_sm.erl	82.71% <0.00%> (+0.33%)	⬆️
src/wpool/mongoose_wpool.erl	85.00% <0.00%> (+1.00%)	⬆️
src/mam/mod_mam_elasticsearch_arch.erl	88.39% <0.00%> (+1.78%)	⬆️
... and 3 more

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[chrzaszcz]

Looks good