fix(microservices): ensure all redis connections are closed

[yatin166]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

Redis connection were not properly closed for pub/sub client due to missing async/await

Issue Number: N/A

What is the new behavior?

Added async/await when quit() is called for pub/sub client for server-redis so that all the connections are properly closed.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[coveralls]

Pull Request Test Coverage Report for Build 86d5e97b-167a-4f3d-9926-ffc87674aec5

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 88.923%

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Totals
Change from base Build c493f148-f1dd-4b7d-a940-d13270fde234:	0.0%
Covered Lines:	7177
Relevant Lines:	8071

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💛 - Coveralls

[kamilmysliwiec]

LGTM