Don't overwrite existing AgentHostPort by default value if env not set

[cuihaikuo]

Signed-off-by: Cui Haikuo haikuo_cui@shannonai.com

Which problem is this PR solving?

• AgentHostPort is overwritten by default value even though the env not set #473

Short description of the changes

• In ReporterConfig.reporterConfigFromEnv(), if the config struct already has a value and env not set then the default value should not override what's in the struct.

[codecov]

Codecov Report

Merging #474 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #474      +/-   ##
==========================================
+ Coverage    88.1%   88.13%   +0.02%     
==========================================
  Files          59       59              
  Lines        3507     3515       +8     
==========================================
+ Hits         3090     3098       +8     
  Misses        305      305              
  Partials      112      112

Impacted Files	Coverage Δ
config/config_env.go	100% <100%> (ø)	⬆️

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[yurishkuro]

Please use Resolves #123 rather than just linking to a ticket, to allow auto-close on merge.

[yurishkuro]

Please add a test that demonstrates the issue you're trying to address.

[ilylia]

I found this pr, but it looks like the author had forgotten it.
I post a new pr at #513, it resolves the same issue, and with some tests.