:fix: improve event bus observability

[riccardomodanese]

Brief description of the PR.
Add a flag to check if the event bus is conencted or not.

Related Issue
none

Description of the solution adopted
see brief description

Screenshots
none

Any side note on the changes made
none

[codecov]

Codecov Report

Attention: Patch coverage is 42.85714% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 21.09%. Comparing base (ab4b252) to head (7d79862).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #4005   +/-   ##
==========================================
  Coverage      21.08%   21.09%           
  Complexity        10       10           
==========================================
  Files           1954     1954           
  Lines          41429    41430    +1     
  Branches        3801     3801           
==========================================
+ Hits            8737     8739    +2     
+ Misses         32288    32287    -1     
  Partials         404      404           

Files	Coverage Δ
...artemis/plugin/security/MetricsSecurityPlugin.java	0.00% <ø> (ø)
...se/kapua/commons/event/jms/JMSServiceEventBus.java	19.21% <42.85%> (+0.37%)	⬆️