libgo/testsuite: kill sleep process in gotest

libgo/testsuite: kill sleep process in gotest

    This change modifies the "gotest" shell script
    to kill all processes, including "sleep", spawned
    by the timeout subshell. This prevents the sleep
    process from living beyond the gotest process.

    BACKGROUND

    The "gotest" shell script spawns "sleep" processes
    in the background to kill off test cases that run
    past their specified timeout. There are commands
    included that appear to kill the sleep process,
    but they only kill the parent shell, causing the
    sleep process to reparent.

    The orphaned sleep process can cause issues when
    gotest is run under some build systems, such as
    Ninja [0]. The particular issue with Ninja is the
    method it uses to identify terminated processes:
    it creates a pipe, passes the write end to the
    child process, and waits for EOF. In the case of
    libgo/gotest, the orphaned sleep process inherits
    the pipe FD and keeps it open for 4 minutes by
    default.

    [0] https://github.com/martine/ninja

    Reviewed-on: https://go-review.googlesource.com/12227

From-SVN: r226526