Duplicate HTTP query parameters when using Parameter in HTTP Request Defaults

**ncasaux** ([Bug 64268](https://bz.apache.org/bugzilla//show_bug.cgi?id=64268&redirect=false)):
Hello!

I'm facing a weird bug involving:
* User defined variables
* ForEach Controller
* HTTP Request Defaults (Config)
* HTTP Request (Sampler)

I tried to create the simplest testplan to reproduce the issue:

* I have defined a list of 6 user defined values.
* I have a loop which creates 6 HTTP Requests
* I have 2 HTTP Request Default, one outside the loop and one inside the loop. They set different fields (1 path and 1 query parameter)

Now the weird part: for some reason, some of my HTTP requests have their query parameter duplicated:
* Requests 1, 2, 4 and 6 are ALWAYS perfecty fine
* Requests 3 and 5 have ALWAYS their query parameter duplicate

I can't find any logic in this!

Please find attached the testplan. I know that in this test plan, I could move both HTTP Request Default outside the loop to solve this issue. But I can not do that in my real test plan.

Thanks in advance!

Created attachment [testBugHTTPQueryParam.jmx](https://apache.github.io/jmeter-bugzilla-attachments/68/64268/37124/testBugHTTPQueryParam.jmx): simplest test plan to reproduce the issue
testBugHTTPQueryParam.jmx

````xml

false
true
false







continue

false
1

1
1
false


true





key_1
v1
=


key_2
v2
=


key_3
v3
=


key_4
v4
=


key_5
v5
=


key_6
v6
=








false
${key}
=
true
param








6





key
key
true










path_1
6













GET
true
false
true
false







false

saveConfig

true
true
true
true
true
true
true
true
true
false
true
true
false
false
false
true
false
false
false
true
0
true
true
true
true
true
true

````

Severity: normal
OS: All