Disable metrics when active=false

[felixbarny]

No description provided.

[eyalkoren]

Great. Two comments:

1. When active=false is used on startup, users may expect no communication is attempted with the server, so check also before doing the health check.
2. Add a test to this disablement

[codecov-io]

Codecov Report

Merging #653 into master will decrease coverage by 2.52%.
The diff coverage is 53.69%.

@@             Coverage Diff              @@
##             master     #653      +/-   ##
============================================
- Coverage     64.77%   62.24%   -2.53%     
  Complexity       68       68              
============================================
  Files           195      199       +4     
  Lines          8088     7782     -306     
  Branches       1025      959      -66     
============================================
- Hits           5239     4844     -395     
- Misses         2547     2640      +93     
+ Partials        302      298       -4

Impacted Files	Coverage Δ	Complexity Δ
...m/agent/jms/JmsMessageListenerInstrumentation.java	0% <0%> (ø)	0 <0> (?)
...astic/apm/agent/jdbc/StatementInstrumentation.java	50% <0%> (-1.73%)	0 <0> (ø)
.../elastic/apm/agent/jms/BaseJmsInstrumentation.java	0% <0%> (ø)	0 <0> (?)
...m/agent/jms/JmsMessageProducerInstrumentation.java	0% <0%> (ø)	0 <0> (?)
.../elastic/apm/agent/jdbc/helper/JdbcHelperImpl.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...lastic/apm/agent/jms/JmsInstrumentationHelper.java	0% <0%> (ø)	0 <0> (?)
...ic/apm/agent/jms/JmsInstrumentationHelperImpl.java	0% <0%> (ø)	0 <0> (?)
...m/agent/jms/JmsMessageConsumerInstrumentation.java	0% <0%> (ø)	0 <0> (?)
...lastic/apm/agent/logging/LoggingConfiguration.java	92.3% <100%> (+0.12%)	0 <0> (ø)	⬇️
...m/agent/jdbc/PreparedStatementInstrumentation.java	47.61% <50%> (-3.9%)	0 <0> (ø)
... and 30 more

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[felixbarny]

I'm not really sure how to properly test that tbh. Not sure if the effort is worth it, especially as it's not a really critical component.