Spring cloud config retry

[pascalgrimaud]

Fix #13800

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[mraible]

@pascalgrimaud I tested this using the following technique:

1. Pulled your branch, ran npm link, then jhipster jdl reactive-ms.
2. I started Keycloak using jhkeycloakup.
3. I navigated to the gateway app and ran ./gradlew.
4. The app spits out errors, but stays up, until I run jhregistryup, then it connects.

So yes, your branch works. Then, I tried the main branch with the same steps and it works too. Do you have steps to reproduce the issue so I can compare main to this PR?

[pascalgrimaud]

Can you try with prod profile instead of Dev ?

[mraible]

I tried with the prod profile on the main branch (that uses spring.config.import). It fails:

Caused by: org.springframework.web.client.ResourceAccessException: I/O error on GET request for 
"http://localhost:8761/config/gateway/prod/main": Connection refused (Connection refused); 
nested exception is java.net.ConnectException: Connection refused (Connection refused)
        at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:784)
        at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:710)
        at org.springframework.web.client.RestTemplate.exchange(RestTemplate.java:601)
        at org.springframework.cloud.config.client.ConfigServerConfigDataLoader.getRemoteEnvironment(ConfigServerConfigDataLoader.java:252)
        at org.springframework.cloud.config.client.ConfigServerConfigDataLoader.doLoad(ConfigServerConfigDataLoader.java:102)
        ... 25 common frames omitted

If I try with this PR, it works was as expected, and waits for the JHipster Registry to start.

:: JHipster 🤓  :: Running Spring Boot 2.4.2 ::
:: https://www.jhipster.tech ::

<===========--> 90% EXECUTING [1m 45s]

FYI... @spencergibb. We're using org.springframework.cloud:spring-cloud-config-client:3.0.1.