fix: auth module dns resolution and code quality

[Vaishnav88sk]

This PR addresses two critical issues found in the operator/auth module:

1. DNS Resolution Double-Suffix Bug:
   If a user provided a Fully Qualified Domain Name (FQDN) via the reshapr.io/instance annotation that already contained .svc.cluster.local, ReshaprApiClientFactory would append the suffix a second time, resulting in an UnknownHostException. This is now fixed by checking if the suffix already exists.

2. Code Quality / Concurrency Bug:
   In ReshaprAuthenticationService, the exception handler was unconditionally calling Thread.currentThread().interrupt() on IOException. This is a concurrency anti-pattern that can disrupt thread-pool behavior on simple network timeouts. The IOException and InterruptedException catch blocks have been split to properly isolate the thread interruption logic.