Remove redundant sync primitives for metrics (#14564)

* Remove redundant locks

* Re-enable warning for a sender when a queue got processed

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Anton <[email protected]>

* Use debug for subsequent logging

* Update client/network/src/service/out_events.rs

Co-authored-by: Bastian Köcher <[email protected]>

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Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Anton <[email protected]>
Co-authored-by: parity-processbot <>