Relax fd bounds checking

We can cope with fds greater than SocketEngine::GetMaxFds() since 3752b3f59d5216d7dc6221a361efc76b9ad2273d
socketengine_epoll Pass a dummy value to epoll_create() that does not depend on GetMaxFds()

From man epoll:
Since Linux 2.6.8, the size argument is unused, but must be greater than zero. (The kernel dynamically sizes the required data structures without needing this initial hint.)
Change the number reported by SocketEngine::GetMaxFds() to be informal

Do not exit if we can't determine it