#3 Deleting or renaming files invalidates client file handles

[Josh Taylor]

// Rename crash (assume "/foo" is a valid
// file and "/bar" doesn't exist)
int fd = client->Open("/foo", O_RDONLY);
client->Rename("/foo", "/bar");
char buf[256];
client->Read(fd, buf, sizeof(buf)); // crash

// Delete crash (assume "/foo" is a valid file)
int fd = client->Open("/foo", O_RDONLY);
client->Remove("/foo");
char buf[256];
client->Read(fd, buf, sizeof(buf)); // crash