Bring in https://golang.org/cl/98616 from gc tip.
Original CL description:
This change modifies Go to disable loading of users' shell history for
TestTerminalSignal tests. TestTerminalSignal, as part of its workload,
will execute a new interactive bash shell. Bash will attempt to load the
user's history from the file pointed to by the HISTFILE environment
variable. For users with large histories that may take up to several
seconds, pushing the whole test past the 5 second timeout and causing
it to fail.
Reviewed-on: https://go-review.googlesource.com/107624
From-SVN: r259452
