springboot Upgrade to Reactor Californium-SR16

Comment From: wilkinsona

Current Californium snapshots cause a test in spring-boot-actuator to fail:

[INFO] Results:
[INFO] 
[ERROR] Failures: 
[ERROR]   CachingOperationInvokerTests.cacheInTtlWithFluxResponse:94 expected:<[1]> but was:<[2]>
[INFO] 
[ERROR] Tests run: 963, Failures: 1, Errors: 0, Skipped: 0

It appears that Flux caching doesn't work. The following pure Reactor test passes with SR-15 but fails with the current BUILD-SNAPSHOT of Californium:

@Test
public void fluxCaching() {
    AtomicInteger invocations = new AtomicInteger();
    Flux<String> flux = Flux.fromIterable(() -> {
        invocations.incrementAndGet();
        return Arrays.asList("spring", "boot").iterator();
    }).cache(Duration.ofHours(1));
    assertThat(flux.blockLast()).isEqualTo("boot");
    assertThat(flux.blockLast()).isEqualTo("boot");
    assertThat(invocations).hasValue(1);
}

The test fails because the value of invocations is two.