POC for fabric8io/kubernetes-client#6059

To reproduce the issue, just run the project (you may want to change namespacename and podname in DemoApplication.java even if the bug also happens if the pod does not exist) : mvn spring-boot:run.
You will have the following non-blocking error message :

java.util.concurrent.CompletionException: java.util.concurrent.RejectedExecutionException
	at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:315) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:320) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1159) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2179) ~[na:na]
	at io.fabric8.kubernetes.client.http.StandardHttpClient.lambda$completeOrCancel$10(StandardHttpClient.java:142) ~[kubernetes-client-api-6.13.0.jar:na]
	at java.base/java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:863) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:841) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2179) ~[na:na]
	at io.fabric8.kubernetes.client.http.ByteArrayBodyHandler.onBodyDone(ByteArrayBodyHandler.java:51) ~[kubernetes-client-api-6.13.0.jar:na]
	at java.base/java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:863) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:841) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:510) ~[na:na]
	at java.base/java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:2179) ~[na:na]
	at io.fabric8.kubernetes.client.okhttp.OkHttpClientImpl$OkHttpAsyncBody.doConsume(OkHttpClientImpl.java:136) ~[kubernetes-httpclient-okhttp-6.13.0.jar:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[na:na]
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[na:na]
	at java.base/java.lang.Thread.run(Thread.java:1583) ~[na:na]
Caused by: java.util.concurrent.RejectedExecutionException: null
	at io.fabric8.kubernetes.client.utils.internal.SerialExecutor.execute(SerialExecutor.java:47) ~[kubernetes-client-6.13.0.jar:na]
	at io.fabric8.kubernetes.client.informers.impl.cache.SharedProcessor.execute(SharedProcessor.java:179) ~[kubernetes-client-6.13.0.jar:na]
	at io.fabric8.kubernetes.client.informers.impl.cache.Reflector.lambda$null$4(Reflector.java:136) ~[kubernetes-client-6.13.0.jar:na]
	at io.fabric8.kubernetes.client.informers.impl.cache.ProcessorStore.retainAll(ProcessorStore.java:116) ~[kubernetes-client-6.13.0.jar:na]
	at io.fabric8.kubernetes.client.informers.impl.cache.Reflector.lambda$listSyncAndWatch$6(Reflector.java:130) ~[kubernetes-client-6.13.0.jar:na]
	at java.base/java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:1150) ~[na:na]
	... 16 common frames omitted

Downgrading to fabric8 6.12.0 or older version you will not have this error