Stop NinjaReader from sending new status messages after Close

If NinjsReader keeps sending tool status messages after Close has been
called it can cause a concurrent map access when
CriticalPath.WriteToMetrics is called concurrently with
CriticalPath.FinishAction.  Try harder to stop the NinjaReader goroutine
when NinjaReader.Close is called, even if the external ninja process has
not closed its FIFO or NinjaReader has not finished processing all the
messages after 5 seconds.

Bug: 286382228
Test: m nothing
Change-Id: I3e3dce601510e2dfb5ed82ca55bd11723fac7e70