Release connection to pool on connect error

[cyu]

Fix issue where connecting to websocket server that returns request error will hang waiting for connection pool to drain.

[coveralls]

Pull Request Test Coverage Report for Build 137

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 91.459%

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Totals
Change from base Build 135:	-0.3%
Covered Lines:	257
Relevant Lines:	281

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💛 - Coveralls

[ioquatix]

Thanks for this. I'm going to merge it but some more changes might be required.

[ioquatix]

It was released in v0.15.0, sorry for the delay.