This test reveals the patters of the batching of consecutive write
operations on a file-system session. It issues 100 writes of one byte
each, which should ideally result in large batches of operations
submitted to the file-system session at once.
The run script performs the write operations through a chain of two VFS
servers, thereby exercising the write batching of both the libc and the
intermediate VFS server.
Issue #4697
