CAMEL-22527: Fix flaky HttpRouteTest and JettyFailoverRoundRobinTest

[gnodet]

CAMEL-22527

Fixes two flaky tests in camel-jetty:

HttpRouteTest.testEchoEndpoint

The enableSessionSupport method in JettyHttpComponent threw IllegalStateException when session support was requested on a Jetty server that was already started (e.g., when another route on the same port was connected first). Instead of throwing, the fix restarts the server to add session support — matching the existing pattern for handler changes. The JettySessionSupportTest is updated to verify the new behavior: session support now works correctly even when added to a port that already has other routes.

JettyFailoverRoundRobinTest.testJettyFailoverRoundRobin

The test assumed the failover round-robin load balancer always starts at index 0, but the starting index can vary depending on the AtomicInteger counter state. The fix verifies that both good endpoints are reached across two requests (confirming both failover and round-robin behavior) without assuming a specific starting index.

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• components/camel-jetty-common
• components/camel-jetty

ℹ️ Dependent modules were not tested because the total number of affected modules exceeded the threshold (50). Use the test-dependents label to force testing all dependents.

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Build reactor — dependencies compiled but only changed modules were tested (2 modules)

• Camel :: Jetty
• Camel :: Jetty :: Common

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