RADAS: change the request_queue to request_channel in config

[ligangty]

As topic is also a valid destination to send, use queue is not
correct

[coveralls]

Pull Request Test Coverage Report for Build 15467292369

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 4 of 5 (80.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 66.647%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
charon/config.py	3	4	75.0%

Totals
Change from base Build 15462656168:	0.0%
Covered Lines:	2218
Relevant Lines:	3328

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💛 - Coveralls