BatcherImplTest is flaky

[blakeli0]

BatcherImplTest sometimes fails with the following log:

com.google.api.gax.batching.BatcherImplTest > testThrottlingBlocking FAILED
    org.mockito.exceptions.base.MockitoException: 
    No argument value was captured!
    You might have forgotten to use argument.capture() in verify()...
    ...or you used capture() in stubbing but stubbed method was not called.
    Be aware that it is recommended to use capture() only with verify()
    Examples of correct argument capturing:
        ArgumentCaptor<Person> argument = ArgumentCaptor.forClass(Person.class);
        verify(mock).doSomething(argument.capture());
        assertEquals("John", argument.getValue().getName());
        at com.google.api.gax.batching.BatcherImplTest.testThrottlingBlocking(BatcherImplTest.java:895)

[blakeli0]

Duplicate of #1615