Enable keep-alive for provisioning socket

[gferon]

Just found this while starting to look into linking errors.

Reference: https://github.com/signalapp/Signal-Desktop/blob/c6c072319993fefd9fcfab55ca77dc75263bc875/ts/textsecure/SocketManager.ts#L273

[codecov[bot]]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (34ad911) 3.65% compared to head (a1429c9) 3.65%.

Files	Patch %	Lines
libsignal-service-actix/src/push_service.rs	0.00%	2 Missing :warning:
libsignal-service-hyper/src/push_service.rs	0.00%	2 Missing :warning:
libsignal-service/src/websocket.rs	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #269 +/- ## ===================================== Coverage 3.65% 3.65% ===================================== Files 38 38 Lines 2818 2818 ===================================== Hits 103 103 Misses 2715 2715 ```

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[rubdos]

Are there no ws's anymore without KA? If so, don't forget to also amend actix :-)

[gferon]

True dat, and yes they're all with keep alive.