LazyCloseableTest.testOpensLazilyExactlyOnceThreaded intermittently fails with: collection size <8> was less than <10>

[alecgrieser]

I've seen a few instances of LazyCloseableTest.testOpensLazilyExactlyOnceThreaded fail in CI, including blocking at least one release build. The last time, it failed with the following assertion error:

LazyCloseableTest > testOpensLazilyExactlyOnceThreaded() FAILED
    java.lang.AssertionError: 
    Expected: a collection with size a value greater than <10>
         but: collection size <8> was less than <10>
        at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
        at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:6)
        at com.apple.foundationdb.record.lucene.codec.LazyCloseableTest.testOpensLazilyExactlyOnceThreaded(LazyCloseableTest.java:94)

I'm not sure if we've seen PRBs fail with this, too, but it could be a source of build instability.