veyron/examples/tunnel: Fix possible "send on closed channel" error.

This is an attempt to fix a race that sometimes leads to a panic of the form:
panic: runtime error: send on closed channel

goroutine 71 [running]:
runtime.panic(0x3c6098, 0x60734e)
	/usr/local/google/home/andreser/veyron/environment/go/src/pkg/runtime/panic.c:279 +0x1a0
veyron/examples/tunnel/tunneld/impl.(*ioManager).stdout2outchan(0x10a2bd70)

Change-Id: I1cb048a09b38defd0f7f06540f05df1d647e234c
2 files changed
tree: e29ba2ad09e2a76739d858daa80068b90ba224f1
  1. lib/
  2. tunneld/
  3. vsh/
  4. tunnel.vdl
  5. tunnel.vdl.go