unix: correct error when calling uv_shutdown twice

This is a backport of a284b90 for v0.10 branch
windows: freeze in uv_tcp_endgame

The event_handle field of unused accept requests was not being
initialized properly. As a result, uv_tcp_endgame would try to close
an invalid handle and this could lead to unexpected behavior.

This fixes node.js test test-cluster-disconnect.js on Windows.
Merge branch 'v0.10'

Conflicts:
	build.mk
	test/test-shutdown-twice.c