firestore.it.ITSystemTest.testRecursiveDeleteDoesNotAffectOtherCollections failed

[zhumin8]

observed in pr, see failed log for details.

ITSystemTest(sponge_log).testRecursiveDeleteDoesNotAffectOtherCollectionscontent_copy | - | 2.286s
-- | -- | --
java.lang.AssertionError: expected:<0> but was:<1>	at org.junit.Assert.fail(Assert.java:89)	at org.junit.Assert.failNotEquals(Assert.java:835)	at org.junit.Assert.assertEquals(Assert.java:647)

ITSystemTest(sponge_log).testRecursiveDeleteDoesNotAffectOtherCollections
-	2.286s
java.lang.AssertionError: expected:<0> but was:<1>
	at org.junit.Assert.fail(Assert.java:89)
	at org.junit.Assert.failNotEquals([Assert.java:835](https://cs.corp.google.com/piper///depot/google3/third_party/java_src/junit/main/java/org/junit/Assert.java?q=fail&l=835&ws&snapshot=0))
	at org.junit.Assert.assertEquals([Assert.java:647](https://cs.corp.google.com/piper///depot/google3/third_party/java_src/junit/main/java/org/junit/Assert.java?q=failNotEquals&l=647&ws&snapshot=0))