close[t:4367] Make the test tolerate the case where the number of calls to pwrite is small and the test wasn't aborting.  Now it aborts if the number of calls is smaller than the -C argument.  Fix #4376.

git-svn-id: file:///svn/toku/tokudb@38591 c7de825b-a66e-492c-adef-691d508d4ae1